Method and Apparatus for Uplink Transmission and Reception in a Wireless Communication System

ABSTRACT

Disclosed are a method for transmitting and receiving an uplink in a wireless communication system and an apparatus therefore. Specifically, a method for uplink transmission by a User Equipment (UE) in a wireless communication system may include: receiving, from a base station, Sounding Reference Signal (SRS) configuration information, wherein the SRS configuration information includes a parameter set for power control of SRS for each SRS resource set and the SRS resource set includes one or more SRS resources; determining a transmission power of the SRS, based on the parameter set for power control of the SRS; and transmitting the SRS to the base station.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for uplink transmission/reception andtransmission power control and an apparatus for supporting the same.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An object of the present invention is to propose a method fortransmitting/receiving an uplink signal (e.g., SRS)/channel (e.g.,physical uplink control channel (PUCCH) and physical uplink sharedchannel (PUSCH), in particular, a transmission power control of anuplink signal/channel.

Further, an object of the present invention is to propose an uplinkpower control method for multiple sounding reference signals (SRS).

The technical objects of the present invention are not limited to theaforementioned technical objects, and other technical objects, which arenot mentioned above, will be apparently appreciated by a person havingordinary skill in the art from the following description.

Technical Solution

In an aspect of the present invention, a method for uplink transmissionby a User Equipment (UE) in a wireless communication system may include:receiving, from a base station, Sounding Reference Signal (SRS)configuration information, wherein the SRS configuration informationincludes a parameter set for power control of SRS for each SRS resourceset and the SRS resource set includes one or more SRS resources;determining a transmission power of the SRS, based on the parameter setfor power control of the SRS; and transmitting the SRS to the basestation.

In another aspect of the present invention, a user equipment (UE)performing uplink transmission in a wireless communication system mayinclude: a transceiver for transmitting and receiving a radio signal;and a processor for controlling the transceiver, in which the processormay be configured to receive, from a base station, Sounding ReferenceSignal (SRS) configuration information, wherein the SRS configurationinformation includes a parameter set for power control of SRS for eachSRS resource set and the SRS resource set includes one or more SRSresources; determine a transmission power of the SRS, based on theparameter set for power control of the SRS; and transmit the SRS to thebase station.

Preferably, the transmission power of the SRS may be determined, basedon a downlink path-loss estimation value calculated by the UE using adownlink reference signal indicated by the parameter set for the powercontrol of the SRS.

Preferably, the downlink reference signal may include SynchronizationSignal Block (SSB) and Channel State Information-Reference Signal(CSI-RS).

Preferably, the downlink reference signal is changed by a Medium AccessControl-Control Element (MAC-CE) transmitted by the base station.

Preferably, the transmission power of the SRS may be determined byapplying a Transmit Power Control (TPC) accumulation commonly to the SRSresource set.

Preferably, a power control adjustment for adjusting the transmissionpower of the SRS may be applied independently for each specific SRStransmission interval.

Preferably, when the power control adjustment is triggered, all oftransmission power values of the SRS may be identically adjusted on allSRS resources, regardless of the transmission power of the SRS beingdetermined.

Preferably, when the adjusted transmission power value exceeds apredetermined value, the adjusted transmission power value may be scaleddown collectively.

Preferably, the method may further include: receiving, from the basestation, downlink control information (DCI) including Physical UplinkShared Channel (PUSCH) scheduling information, wherein the DCI includesa SRS Resource Indicator (SRI); determining a PUSCH transmission powerbased on a parameter set for power control of PUSCH determined from theSRI; and transmitting the PUSCH to the base station.

Preferably, when a plurality of SRS resources are indicated by the SRIand a layer group is configured differently for each of the plurality ofSRS resources, a parameter set for power control of the PUSCH may berespectively determined for each layer group.

Preferably, the transmission power of the PUSCH may be determined, basedon a downlink path-loss estimation value calculated by the UE using adownlink reference signal indicated by the parameter set for the powercontrol of the PUSCH.

Preferably, the downlink reference signal may be changed by a MediumAccess Control-Control Element (MAC-CE) transmitted by the base station.

Preferably, the method may further include: determining a transmissionpower of Physical Uplink Shared Channel (PUSCH) based on a downlinkpath-loss estimation value calculated by the UE using a downlinkreference signal; and transmitting the PUSCH to the base station, inwhich when information for the downlink reference signal is not providedby the base station, the path-loss estimation value may be calculatedusing a downlink reference signal having a relatively largest powerlevel.

Advantageous Effects

According to an embodiment of the present invention, a transmissionpower can be efficiently controlled when an uplink signal/channel istransmitted.

Furthermore, according to an embodiment of the present invention, thetransmission power can be efficiently controlled when the uplinksignal/channel is transmitted in a situation in which a plurality of SRSresources is configured.

Advantages which can be obtained in the present invention are notlimited to the aforementioned effects and other unmentioned advantageswill be clearly understood by those skilled in the art from thefollowing description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included herein as a part of thedescription for help understanding the present invention, provideembodiments of the present invention, and describe the technicalfeatures of the present invention with the description below.

FIG. 1 illustrates the structure of a radio frame in a wirelesscommunication system to which the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for a downlink slot ina wireless communication system to which the present invention may beapplied.

FIG. 3 illustrates a structure of downlink subframe in a wirelesscommunication system to which the present invention may be applied.

FIG. 4 illustrates a structure of uplink subframe in a wirelesscommunication system to which the present invention may be applied.

FIG. 5 illustrates the configuration of a known MIMO communicationsystem.

FIG. 6 is a diagram showing a channel from a plurality of transmissionantennas to a single reception antenna.

FIG. 7 illustrates reference signal patterns mapped to downlink resourceblock pairs in a wireless communication system to which the presentinvention may be applied.

FIG. 8 is a diagram illustrating resources to which reference signalsare mapped in a wireless communication system to which the presentinvention may be applied.

FIG. 9 illustrates an uplink subframe including a sounding referencesignal symbol in a wireless communication system to which the presentinvention may be applied.

FIG. 10 is a diagram illustrating a self-contained subframe structure inthe wireless communication system to which the present invention may beapplied.

FIG. 11 illustrates a transceiver unit model in the wirelesscommunication system to which the present invention may be applied.

FIG. 12 is a diagram illustrating a service area for each transceiverunit in the wireless communication system to which the present inventionmay be applied.

FIG. 13 is a diagram illustrating a method for transmitting andreceiving an uplink according to an embodiment of the present invention.

FIG. 14 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present invention.

MODE FOR INVENTION

Some embodiments of the present invention are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings are intended to describesome embodiments of the present invention and are not intended todescribe a sole embodiment of the present invention. The followingdetailed description includes more details in order to provide fullunderstanding of the present invention. However, those skilled in theart will understand that the present invention may be implementedwithout such more details.

In some cases, in order to avoid that the concept of the presentinvention becomes vague, known structures and devices are omitted or maybe shown in a block diagram form based on the core functions of eachstructure and device.

In this specification, a base station has the meaning of a terminal nodeof a network over which the base station directly communicates with adevice. In this document, a specific operation that is described to beperformed by a base station may be performed by an upper node of thebase station according to circumstances. That is, it is evident that ina network including a plurality of network nodes including a basestation, various operations performed for communication with a devicemay be performed by the base station or other network nodes other thanthe base station. The base station (BS) may be substituted with anotherterm, such as a fixed station, a Node B, an eNB (evolved-NodeB), a BaseTransceiver System (BTS), or an access point (AP). Furthermore, thedevice may be fixed or may have mobility and may be substituted withanother term, such as User Equipment (UE), a Mobile Station (MS), a UserTerminal (UT), a Mobile Subscriber Station (MSS), a Subscriber Station(SS), an Advanced Mobile Station (AMS), a Wireless Terminal (WT), aMachine-Type Communication (MTC) device, a Machine-to-Machine (M2M)device, or a Device-to-Device (D2D) device.

Hereinafter, downlink (DL) means communication from an eNB to UE, anduplink (UL) means communication from UE to an eNB. In DL, a transmittermay be part of an eNB, and a receiver may be part of UE. In UL, atransmitter may be part of UE, and a receiver may be part of an eNB.

Specific terms used in the following description have been provided tohelp understanding of the present invention, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present invention.

The following technologies may be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), and Non-OrthogonalMultiple Access (NOMA). CDMA may be implemented using a radiotechnology, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asGlobal System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data rates for GSM Evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of a UniversalMobile Telecommunications System (UMTS). 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of an Evolved UMTS(E-UMTS) using evolved UMTS Terrestrial Radio Access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-Advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present invention and that are not described in orderto clearly expose the technical spirit of the present invention may besupported by the documents. Furthermore, all terms disclosed in thisdocument may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A or new RAT (RATin 5G (5 generation) system) is chiefly described, but the technicalcharacteristics of the present invention are not limited thereto.

General System to which the Present Invention May be Applied

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a radio frame structure type 1 which may beapplicable to Frequency Division Duplex (FDD) and a radio framestructure which may be applicable to Time Division Duplex (TDD).

The size of a radio frame in the time domain is represented as amultiple of a time unit of T_s=1/(15000*2048). A UL and DL transmissionincludes the radio frame having a duration of T_f=307200*T_s=10 ms.

FIG. 1(a) exemplifies a radio frame structure type 1. The type 1 radioframe may be applied to both of full duplex FDD and half duplex FDD.

A radio frame includes 10 subframes. A radio frame includes 20 slots ofT_slot=15360*T_s=0.5 ms length, and 0 to 19 indexes are given to each ofthe slots. One subframe includes consecutive two slots in the timedomain, and subframe i includes slot 2i and slot 2i+1. The time requiredfor transmitting a subframe is referred to as a transmission timeinterval (TTI). For example, the length of the subframe i may be 1 msand the length of a slot may be 0.5 ms.

A UL transmission and a DL transmission l the FDD are distinguished inthe frequency domain. Whereas there is no restriction in the full duplexFDD, a UE may not transmit and receive simultaneously in the half duplexFDD operation.

One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in the time domain and includes a pluralityof Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, OFDMsymbols are used to represent one symbol period because OFDMA is used indownlink. An OFDM symbol may be called one SC-FDMA symbol or symbolperiod. An RB is a resource allocation unit and includes a plurality ofcontiguous subcarriers in one slot.

FIG. 1(b) shows frame structure type 2.

A type 2 radio frame includes two half frame of 153600*T_s=5 ms lengtheach. Each half frame includes 5 subframes of 30720*T_s=1 ms length.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes.

Table 1 shows the uplink-downlink configuration.

TABLE 1 Downlink- to-Uplink Uplink- Switch- Downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

Referring to Table 1, in each subframe of the radio frame, CD′represents a subframe for a DL transmission, ‘U’ represents a subframefor UL transmission, and CS' represents a special subframe includingthree types of fields including a Downlink Pilot Time Slot (DwPTS), aGuard Period (GP), and a Uplink Pilot Time Slot (UpPTS).

A DwPTS is used for an initial cell search, synchronization or channelestimation in a UE. A UpPTS is used for channel estimation in an eNB andfor synchronizing a UL transmission synchronization of a UE. A GP isduration for removing interference occurred in a UL owing to multi-pathdelay of a DL signal between a UL and a DL.

Each subframe i includes slot 2i and slot 2i+1 of T_slot=15360*T_s=0.5ms.

The UL-DL configuration may be classified into 7 types, and the positionand/or the number of a DL subframe, a special subframe and a UL subframeare different for each configuration.

A point of time at which a change is performed from downlink to uplinkor a point of time at which a change is performed from uplink todownlink is called a switching point. The periodicity of the switchingpoint means a cycle in which an uplink subframe and a downlink subframeare changed is identically repeated. Both 5 ms and 10 ms are supportedin the periodicity of a switching point. If the periodicity of aswitching point has a cycle of a 5 ms downlink-uplink switching point,the special subframe S is present in each half frame. If the periodicityof a switching point has a cycle of a 5 ms downlink-uplink switchingpoint, the special subframe S is present in the first half frame only.

In all the configurations, 0 and 5 subframes and a DwPTS are used foronly downlink transmission. An UpPTS and a subframe subsequent to asubframe are always used for uplink transmission.

Such uplink-downlink configurations may be known to both an eNB and UEas system information. An eNB may notify UE of a change of theuplink-downlink allocation state of a radio frame by transmitting onlythe index of uplink-downlink configuration information to the UEwhenever the uplink-downlink configuration information is changed.Furthermore, configuration information is kind of downlink controlinformation and may be transmitted through a Physical Downlink ControlChannel (PDCCH) like other scheduling information. Configurationinformation may be transmitted to all UEs within a cell through abroadcast channel as broadcasting information.

Table 2 represents configuration (length of DwPTS/GP/UpPTS) of a specialsubframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Special cyclic cyclic cyclicExtended subframe prefix in prefix prefix in cyclic prefix configurationDwPTS uplink in uplink DwPTS uplink in uplink 0  6592 · T_(s) 2192 ·T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of a radio subframe according to the example of FIG. 1 isjust an example, and the number of subcarriers included in a radioframe, the number of slots included in a subframe and the number of OFDMsymbols included in a slot may be changed in various manners.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

Referring to FIG. 2, one downlink slot includes a plurality of OFDMsymbols in a time domain. It is described herein that one downlink slotincludes 7 OFDMA symbols and one resource block includes 12 subcarriersfor exemplary purposes only, and the present invention is not limitedthereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberof RBs N^(∧)DL included in a downlink slot depends on a downlinktransmission bandwidth.

The structure of an uplink slot may be the same as that of a downlinkslot.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 3, a maximum of three OFDM symbols located in a frontportion of a first slot of a subframe correspond to a control region inwhich control channels are allocated, and the remaining OFDM symbolscorrespond to a data region in which a physical downlink shared channel(PDSCH) is allocated. Downlink control channels used in 3GPP LTEinclude, for example, a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid-ARQ indicator channel (PHICH).

A PCFICH is transmitted in the first OFDM symbol of a subframe andcarries information about the number of OFDM symbols (i.e., the size ofa control region) which is used to transmit control channels within thesubframe. A PHICH is a response channel for uplink and carries anacknowledgement (ACK)/not-acknowledgement (NACK) signal for a HybridAutomatic Repeat Request (HARQ). Control information transmitted in aPDCCH is called Downlink Control Information (DCI). DCI includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for aspecific UE group.

A PDCCH may carry information about the resource allocation andtransport format of a downlink shared channel (DL-SCH) (this is alsocalled an “downlink grant”), resource allocation information about anuplink shared channel (UL-SCH) (this is also called a “uplink grant”),paging information on a PCH, system information on a DL-SCH, theresource allocation of a higher layer control message, such as a randomaccess response transmitted on a PDSCH, a set of transmission powercontrol commands for individual UE within specific UE group, and theactivation of a Voice over Internet Protocol (VoIP), etc. A plurality ofPDCCHs may be transmitted within the control region, and UE may monitora plurality of PDCCHs. A PDCCH is transmitted on a single ControlChannel Element (CCE) or an aggregation of some contiguous CCEs. A CCEis a logical allocation unit that is used to provide a PDCCH with acoding rate according to the state of a radio channel. A CCE correspondsto a plurality of resource element groups. The format of a PDCCH and thenumber of available bits of a PDCCH are determined by an associationrelationship between the number of CCEs and a coding rate provided byCCEs.

An eNB determines the format of a PDCCH based on DCI to be transmittedto UE and attaches a Cyclic Redundancy Check (CRC) to controlinformation. A unique identifier (a Radio Network Temporary Identifier(RNTI)) is masked to the CRC depending on the owner or use of a PDCCH.If the PDCCH is a PDCCH for specific UE, an identifier unique to the UE,for example, a Cell-RNTI (C-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for a paging message, a paging indication identifier, forexample, a Paging-RNTI (P-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for system information, more specifically, a SystemInformation Block (SIB), a system information identifier, for example, aSystem Information-RNTI (SI-RNTI) may be masked to the CRC. A RandomAccess-RNTI (RA-RNTI) may be masked to the CRC in order to indicate arandom access response which is a response to the transmission of arandom access preamble by UE.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 4, the uplink subframe may be divided into a controlregion and a data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) carrying uplink control information is allocatedto the control region. A physical uplink shared channel (PUSCH) carryinguser data is allocated to the data region. In order to maintain singlecarrier characteristic, one UE does not send a PUCCH and a PUSCH at thesame time.

A Resource Block (RB) pair is allocated to a PUCCH for one UE within asubframe. RBs belonging to an RB pair occupy different subcarriers ineach of 2 slots. This is called that an RB pair allocated to a PUCCH isfrequency-hopped in a slot boundary.

Multi-Input Multi-Output (MIMO)

A MIMO technology does not use single transmission antenna and singlereception antenna that have been commonly used so far, but uses amulti-transmission (Tx) antenna and a multi-reception (Rx) antenna. Inother words, the MIMO technology is a technology for increasing acapacity or enhancing performance using multi-input/output antennas inthe transmission end or reception end of a wireless communicationsystem. Hereinafter, MIMO is called a “multi-input/output antenna.”.

More specifically, the multi-input/output antenna technology does notdepend on a single antenna path in order to receive a single totalmessage and completes total data by collecting a plurality of datapieces received through several antennas. As a result, themulti-input/output antenna technology can increase a data transfer ratewithin a specific system range and can also increase a system rangethrough a specific data transfer rate.

It is expected that an efficient multi-input/output antenna technologywill be used because next-generation mobile communication requires adata transfer rate much higher than that of existing mobilecommunication. In such a situation, the MIMO communication technology isa next-generation mobile communication technology which may be widelyused in mobile communication UE and a relay node and has been in thespotlight as a technology which may overcome a limit to the transferrate of another mobile communication attributable to the expansion ofdata communication.

Meanwhile, the multi-input/output antenna (MIMO) technology of varioustransmission efficiency improvement technologies that are beingdeveloped has been most in the spotlight as a method capable ofsignificantly improving a communication capacity andtransmission/reception performance even without the allocation ofadditional frequencies or a power increase.

FIG. 5 shows the configuration of a known MIMO communication system.

Referring to FIG. 5, if the number of transmission (Tx) antennas isincreased to N_T and the number of reception (Rx) antennas is increasedto N_R at the same time, a theoretical channel transmission capacity isincreased in proportion to the number of antennas, unlike in the casewhere a plurality of antennas is used only in a transmitter or areceiver. Accordingly, a transfer rate can be improved, and frequencyefficiency can be significantly improved. In this case, a transfer rateaccording to an increase of a channel transmission capacity may betheoretically increased by a value obtained by multiplying the followingrate increment R_i by a maximum transfer rate R_o if one antenna isused.

R _(i)=min(N _(T) ,N _(R))  [Equation 1]

That is, in an MIMO communication system using 4 transmission antennasand 4 reception antennas, for example, a quadruple transfer rate can beobtained theoretically compared to a single antenna system.

Such a multi-input/output antenna technology may be divided into aspatial diversity method for increasing transmission reliability usingsymbols passing through various channel paths and a spatial multiplexingmethod for improving a transfer rate by sending a plurality of datasymbols at the same time using a plurality of transmission antennas.Furthermore, active research is being recently carried out on a methodfor properly obtaining the advantages of the two methods by combiningthe two methods.

Each of the methods is described in more detail below.

First, the spatial diversity method includes a space-time blockcode-series method and a space-time Trelis code-series method using adiversity gain and a coding gain at the same time. In general, theTrelis code-series method is better in terms of bit error rateimprovement performance and the degree of a code generation freedom,whereas the space-time block code-series method has low operationalcomplexity. Such a spatial diversity gain may correspond to an amountcorresponding to the product (N_T×N_R) of the number of transmissionantennas (N_T) and the number of reception antennas (N_R).

Second, the spatial multiplexing scheme is a method for sendingdifferent data streams in transmission antennas. In this case, in areceiver, mutual interference is generated between data transmitted by atransmitter at the same time. The receiver removes the interferenceusing a proper signal processing scheme and receives the data. A noiseremoval method used in this case may include a Maximum LikelihoodDetection (MLD) receiver, a Zero-Forcing (ZF) receiver, a Minimum MeanSquare Error (MMSE) receiver, Diagonal-Bell Laboratories LayeredSpace-Time (D-BLAST), and Vertical-Bell Laboratories Layered Space-Time(V-BLAST). In particular, if a transmission end can be aware of channelinformation, a Singular Value Decomposition (SVD) method may be used.

Third, there is a method using a combination of a spatial diversity andspatial multiplexing. If only a spatial diversity gain is to beobtained, a performance improvement gain according to an increase of adiversity disparity is gradually saturated. If only a spatialmultiplexing gain is used, transmission reliability in a radio channelis deteriorated. Methods for solving the problems and obtaining the twogains have been researched and may include a double space-time transmitdiversity (double-STTD) method and a space-time bit interleaved codedmodulation (STBICM).

In order to describe a communication method in a multi-input/outputantenna system, such as that described above, in more detail, thecommunication method may be represented as follows through mathematicalmodeling.

First, as shown in FIG. 5, it is assumed that N_T transmission antennasand NR reception antennas are present.

First, a transmission signal is described below. If the N_T transmissionantennas are present as described above, a maximum number of pieces ofinformation which can be transmitted are N_T, which may be representedusing the following vector.

s=[s ₁ ,s ₂ , . . . ,s _(N) _(T) ]^(T)  [Equation 2]

Meanwhile, transmission power may be different in each of pieces oftransmission information s_1, s_2, . . . , s_NT. In this case, if piecesof transmission power are P_1, P_2, . . . , P_NT, transmissioninformation having controlled transmission power may be representedusing the following vector.

ŝ=[ŝ ₁ ,ŝ ₂ , . . . ,ŝ _(N) _(T) ]^(T)=[P ₁ s ₁ ,P ₂ s ₂ , . . . ,P _(N)_(T) s _(N) _(T) ]^(T)  [Equation 3]

Furthermore, transmission information having controlled transmissionpower in the Equation 3 may be represented as follows using the diagonalmatrix P of transmission power.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Meanwhile, the information vector having controlled transmission powerin the Equation 4 is multiplied by a weight matrix W, thus forming N_Ttransmission signals x_1, x_2, . . . , x_NT that are actuallytransmitted. In this case, the weight matrix functions to properlydistribute the transmission information to antennas according to atransport channel condition. The following may be represented using thetransmission signals x_1, x_2, . . . , x_NT.

$\begin{matrix}{x = {\quad{\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix} = {{\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1N_{T}} \\w_{21} & w_{22} & \ldots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\; \hat{s}} = {WPs}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In this case, w_ij denotes weight between an i-th transmission antennaand a j-th transmission information, and W is an expression of a matrixof the weight. Such a matrix W is called a weight matrix or precodingmatrix.

Meanwhile, the transmission signal x, such as that described above, maybe considered to be used in a case where a spatial diversity is used anda case where spatial multiplexing is used.

If spatial multiplexing is used, all the elements of the informationvectors have different values because different signals are multiplexedand transmitted. In contrast, if the spatial diversity is used, all theelements of the information vector s have the same value because thesame signals are transmitted through several channel paths.

A method of mixing spatial multiplexing and the spatial diversity may betaken into consideration. In other words, the same signals may betransmitted using the spatial diversity through 3 transmission antennas,for example, and the remaining different signals may be spatiallymultiplexed and transmitted.

If N_R reception antennas are present, the reception signals y_1, y_2, .. . , y_NR of the respective antennas are represented as follows using avector y.

y=[y ₁ ,y ₂ , . . . ,y _(N) _(R) ]^(T)  [Equation 6]

Meanwhile, if channels in a multi-input/output antenna communicationsystem are modeled, the channels may be classified according totransmission/reception antenna indices. A channel passing through areception antenna i from a transmission antenna j is represented ash_ij. In this case, it is to be noted that in order of the index ofh_ij, the index of a reception antenna comes first and the index of atransmission antenna then comes.

Several channels may be grouped and expressed in a vector and matrixform. For example, a vector expression is described below.

FIG. 6 is a diagram showing a channel from a plurality of transmissionantennas to a single reception antenna.

As shown in FIG. 6, a channel from a total of N_T transmission antennasto a reception antenna i may be represented as follows.

h _(i) ^(T)=[h _(i1) ,h _(i2) , . . . ,h _(iN) _(T) ]  [Equation 7]

Furthermore, if all channels from the N_T transmission antenna to NRreception antennas are represented through a matrix expression, such asEquation 7, they may be represented as follows.

$\begin{matrix}{H = {\quad{\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Meanwhile, Additive White Gaussian Noise (AWGN) is added to an actualchannel after the actual channel experiences the channel matrix H.Accordingly, AWGN n_1, n_2, . . . , n_NR added to the N_R receptionantennas, respectively, are represented using a vector as follows.

n=[n ₁ ,n ₂ , . . . ,n _(N) _(R) ]^(T)  [Equation 9]

A transmission signal, a reception signal, a channel, and AWGN in amulti-input/output antenna communication system may be represented tohave the following relationship through the modeling of the transmissionsignal, reception signal, channel, and AWGN, such as those describedabove.

$\begin{matrix}{y = {\quad{\begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix} = {{{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}} = {{Hx} + n}}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Meanwhile, the number of rows and columns of the channel matrix Hindicative of the state of channels is determined by the number oftransmission/reception antennas. In the channel matrix H, as describedabove, the number of rows becomes equal to the number of receptionantennas N_R, and the number of columns becomes equal to the number oftransmission antennas N_T. That is, the channel matrix H becomes anN_R×N_T matrix.

In general, the rank of a matrix is defined as a minimum number of thenumber of independent rows or columns. Accordingly, the rank of thematrix is not greater than the number of rows or columns. As for figuralstyle, for example, the rank H of the channel matrix H is limited asfollows.

rank(H)≤min(N _(T) ,N _(R))  [Equation 11]

Furthermore, if a matrix is subjected to Eigen value decomposition, arank may be defined as the number of Eigen values that belong to Eigenvalues and that are not 0. Likewise, if a rank is subjected to SingularValue Decomposition (SVD), it may be defined as the number of singularvalues other than 0. Accordingly, the physical meaning of a rank in achannel matrix may be said to be a maximum number on which differentinformation may be transmitted in a given channel.

In this specification, a “rank” for MIMO transmission indicates thenumber of paths through which signals may be independently transmittedat a specific point of time and a specific frequency resource. The“number of layers” indicates the number of signal streams transmittedthrough each path. In general, a rank has the same meaning as the numberof layers unless otherwise described because a transmission end sendsthe number of layers corresponding to the number of ranks used in signaltransmission.

Reference Signal (RS)

In a wireless communication system, a signal may be distorted duringtransmission because data is transmitted through a radio channel. Inorder for a reception end to accurately receive a distorted signal, thedistortion of a received signal needs to be corrected using channelinformation. In order to detect channel information, a method ofdetecting channel information using the degree of the distortion of asignal transmission method and a signal known to both the transmissionside and the reception side when they are transmitted through a channelis chiefly used. The aforementioned signal is called a pilot signal orreference signal (RS).

Furthermore recently, when most of mobile communication systems transmita packet, they use a method capable of improving transmission/receptiondata efficiency by adopting multiple transmission antennas and multiplereception antennas instead of using one transmission antenna and onereception antenna used so far. When data is transmitted and receivedusing multiple input/output antennas, a channel state between thetransmission antenna and the reception antenna must be detected in orderto accurately receive the signal. Accordingly, each transmission antennamust have an individual reference signal.

In a mobile communication system, an RS may be basically divided intotwo types depending on its object. There are an RS having an object ofobtaining channel state information and an RS used for datademodulation. The former has an object of obtaining, by a UE, to obtainchannel state information in the downlink. Accordingly, a correspondingRS must be transmitted in a wideband, and a UE must be capable ofreceiving and measuring the RS although the UE does not receive downlinkdata in a specific subframe. Furthermore, the former is also used forradio resources management (RRM) measurement, such as handover. Thelatter is an RS transmitted along with corresponding resources when aneNB transmits the downlink. A UE may perform channel estimation byreceiving a corresponding RS and thus may demodulate data. Thecorresponding RS must be transmitted in a region in which data istransmitted.

A downlink RS includes one common RS (CRS) for the acquisition ofinformation about a channel state shared by all of UEs within a cell andmeasurement, such as handover, and a dedicated RS (DRS) used for datademodulation for only a specific UE. Information for demodulation andchannel measurement can be provided using such RSs. That is, the DRS isused for only data demodulation, and the CRS is used for the two objectsof channel information acquisition and data demodulation.

The reception side (i.e., UE) measures a channel state based on a CRSand feeds an indicator related to channel quality, such as a channelquality indicator (CQI), a precoding matrix index (PMI) and/or a rankindicator (RI), back to the transmission side (i.e., an eNB). The CRS isalso called a cell-specific RS. In contrast, a reference signal relatedto the feedback of channel state information (CSI) may be defined as aCSI-RS.

The DRS may be transmitted through resource elements if data on a PDSCHneeds to be demodulated. A UE may receive information about whether aDRS is present through a higher layer, and the DRS is valid only if acorresponding PDSCH has been mapped. The DRS may also be called aUE-specific RS or demodulation RS (DMRS).

FIG. 7 illustrates reference signal patterns mapped to downlink resourceblock pairs in a wireless communication system to which the presentinvention may be applied.

Referring to FIG. 7, a downlink resource block pair, that is, a unit inwhich a reference signal is mapped, may be represented in the form ofone subframe in a time domain×12 subcarriers in a frequency domain. Thatis, in a time axis (an x axis), one resource block pair has a length of14 OFDM symbols in the case of a normal cyclic prefix (CP) (FIG. 7a )and has a length of 12 OFDM symbols in the case of an extended cyclicprefix (CP) (FIG. 7b ). In the resource block lattice, resource elements(REs) indicated by “0”, “1”, “2”, and “3” mean the locations of the CRSsof antenna port indices “0”, “1”, “2”, and “3”, respectively, and REsindicated by “D” mean the location of a DRS.

A CRS is described in more detail below. The CRS is a reference signalwhich is used to estimate the channel of a physical antenna and may bereceived by all UEs located within a cell in common. The CRS isdistributed to a full frequency bandwidth. That is, the CRS iscell-specific signal and is transmitted every subframe in a wideband.Furthermore, the CRS may be used for channel quality information (CSI)and data demodulation.

A CRS is defined in various formats depending on an antenna array on thetransmitting side (eNB). In the 3GPP LTE system (e.g., Release-8), an RSfor a maximum four antenna ports is transmitted depending on the numberof transmission antennas of an eNB. The side from which a downlinksignal is transmitted has three types of antenna arrays, such as asingle transmission antenna, two transmission antennas and fourtransmission antennas. For example, if the number of transmissionantennas of an eNB is two, CRSs for a No. 0 antenna port and a No. 1antenna port are transmitted. If the number of transmission antennas ofan eNB is four, CRSs for No. 0 No. 3 antenna ports are transmitted. Ifthe number of transmission antennas of an eNB is four, a CRS pattern inone RB is shown in FIG. 7.

If an eNB uses a single transmission antenna, reference signals for asingle antenna port are arrayed.

If an eNB uses two transmission antennas, reference signals for twotransmission antenna ports are arrayed using a time divisionmultiplexing (TDM) scheme and/or a frequency division multiplexing (FDM)scheme. That is, different time resources and/or different frequencyresources are allocated in order to distinguish between referencesignals for two antenna ports.

Furthermore, if an eNB uses four transmission antennas, referencesignals for four transmission antenna ports are arrayed using the TDMand/or FDM schemes. Channel information measured by the reception side(i.e., UE) of a downlink signal may be used to demodulate datatransmitted using a transmission scheme, such as single transmissionantenna transmission, transmission diversity, closed-loop spatialmultiplexing, open-loop spatial multiplexing or amulti-user-multi-input/output (MIMO) antenna.

If a multi-input multi-output antenna is supported, when a RS istransmitted by a specific antenna port, the RS is transmitted in thelocations of resource elements specified depending on a pattern of theRS and is not transmitted in the locations of resource elementsspecified for other antenna ports. That is, RSs between differentantennas do not overlap.

A DRS is described in more detail below. The DRS is used to demodulatedata. In multi-input multi-output antenna transmission, precoding weightused for a specific UE is combined with a transmission channeltransmitted by each transmission antenna when the UE receives an RS, andis used to estimate a corresponding channel without any change.

A 3GPP LTE system (e.g., Release-8) supports a maximum of fourtransmission antennas, and a DRS for rank 1 beamforming is defined. TheDRS for rank 1 beamforming also indicates an RS for an antenna portindex 5.

In an LTE-A system, that is, an advanced and developed form of the LTEsystem, the design is necessary to support a maximum of eighttransmission antennas in the downlink of an eNB. Accordingly, RSs forthe maximum of eight transmission antennas must be also supported. Inthe LTE system, only downlink RSs for a maximum of four antenna portshas been defined. Accordingly, if an eNB has four to a maximum of eightdownlink transmission antennas in the LTE-A system, RSs for theseantenna ports must be additionally defined and designed. Regarding theRSs for the maximum of eight transmission antenna ports, theaforementioned RS for channel measurement and the aforementioned RS fordata demodulation must be designed.

One of important factors that must be considered in designing an LTE-Asystem is backward compatibility, that is, that an LTE UE must welloperate even in the LTE-A system, which must be supported by the system.From an RS transmission viewpoint, in the time-frequency domain in whicha CRS defined in LTE is transmitted in a full band every subframe, RSsfor a maximum of eight transmission antenna ports must be additionallydefined. In the LTE-A system, if an RS pattern for a maximum of eighttransmission antennas is added in a full band every subframe using thesame method as the CRS of the existing LTE, RS overhead is excessivelyincreased.

Accordingly, the RS newly designed in the LTE-A system is basicallydivided into two types, which include an RS having a channel measurementobject for the selection of MCS or a PMI (channel state information-RSor channel state indication-RS (CSI-RS)) and an RS for the demodulationof data transmitted through eight transmission antennas (datademodulation-RS (DM-RS)).

The CSI-RS for the channel measurement object is characterized in thatit is designed for an object focused on channel measurement unlike theexisting CRS used for objects for measurement, such as channelmeasurement and handover, and for data demodulation. Furthermore, theCSI-RS may also be used for an object for measurement, such as handover.The CSI-RS does not need to be transmitted every subframe unlike the CRSbecause it is transmitted for an object of obtaining information about achannel state. In order to reduce overhead of a CSI-RS, the CSI-RS isintermittently transmitted on the time axis.

For data demodulation, a DM-RS is dedicatedly transmitted to a UEscheduled in a corresponding time-frequency domain. That is, a DM-RS fora specific UE is transmitted only in a region in which the correspondingUE has been scheduled, that is, in the time-frequency domain in whichdata is received.

In the LTE-A system, a maximum of eight transmission antennas aresupported in the downlink of an eNB. In the LTE-A system, if RSs for amaximum of eight transmission antennas are transmitted in a full bandevery subframe using the same method as the CRS in the existing LTE, RSoverhead is excessively increased. Accordingly, in the LTE-A system, anRS has been separated into the CSI-RS of the CSI measurement object forthe selection of MCS or a PMI and the DM-RS for data demodulation, andthus the two RSs have been added. The CSI-RS may also be used for anobject, such as RRM measurement, but has been designed for a main objectfor the acquisition of CSI. The CSI-RS does not need to be transmittedevery subframe because it is not used for data demodulation.Accordingly, in order to reduce overhead of the CSI-RS, the CSI-RS isintermittently transmitted on the time axis. That is, the CSI-RS has aperiod corresponding to a multiple of the integer of one subframe andmay be periodically transmitted or transmitted in a specifictransmission pattern. In this case, the period or pattern in which theCSI-RS is transmitted may be set by an eNB.

For data demodulation, a DM-RS is dedicatedly transmitted to a UEscheduled in a corresponding time-frequency domain. That is, a DM-RS fora specific UE is transmitted only in the region in which scheduling isperformed for the corresponding UE, that is, only in the time-frequencydomain in which data is received.

In order to measure a CSI-RS, a UE must be aware of information aboutthe transmission subframe index of the CSI-RS for each CSI-RS antennaport of a cell to which the UE belongs, the location of a CSI-RSresource element (RE) time-frequency within a transmission subframe, anda CSI-RS sequence.

In the LTE-A system, an eNB has to transmit a CSI-RS for each of amaximum of eight antenna ports. Resources used for the CSI-RStransmission of different antenna ports must be orthogonal. When one eNBtransmits CSI-RSs for different antenna ports, it may orthogonallyallocate the resources according to the FDM/TDM scheme by mapping theCSI-RSs for the respective antenna ports to different REs.Alternatively, the CSI-RSs for different antenna ports may betransmitted according to the CDM scheme for mapping the CSI-RSs topieces of code orthogonal to each other.

When an eNB notifies a UE belonging to the eNB of information on aCSI-RS, first, the eNB must notify the UE of information about atime-frequency in which a CSI-RS for each antenna port is mapped.Specifically, the information includes subframe numbers in which theCSI-RS is transmitted or a period in which the CSI-RS is transmitted, asubframe offset in which the CSI-RS is transmitted, an OFDM symbolnumber in which the CSI-RS RE of a specific antenna is transmitted,frequency spacing, and the offset or shift value of an RE in thefrequency axis.

A CSI-RS is transmitted through one, two, four or eight antenna ports.Antenna ports used in this case are p=15, p=15, 16, p=15, . . . , 18,and p=15, . . . , 22, respectively. A CSI-RS may be defined for only asubcarrier interval Δf=15 kHz.

In a subframe configured for CSI-RS transmission, a CSI-RS sequence ismapped to a complex-valued modulation symbol a_k,l^(∧)(p) used as areference symbol on each antenna port p as in Equation 12.

$\begin{matrix}{\mspace{79mu} {{a_{k,l}^{(p)} = {w_{l^{''}} \cdot {r_{l,n_{s}}\left( m^{\prime} \right)}}}{k = {k^{\prime} + {12m} + \left\{ {{\begin{matrix}{- 0} & {{{{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}},{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 6} & {{{{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 1} & {{{{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 7} & {{{{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 0} & {{{{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}},{{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 3} & {{{{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},{{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 6} & {{{{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},{{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}} \\{- 9} & {{{{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},{{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}}\end{matrix}l} = {l^{\prime} + \left\{ {{\begin{matrix}l^{''} & \begin{matrix}{{{CSI}\mspace{14mu} {reference}\mspace{14mu} {signal}\mspace{14mu} {configurations}\mspace{14mu} 0\text{-}19},} \\{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix} \\{2l^{''}} & \begin{matrix}{{{CSI}\mspace{14mu} {reference}\mspace{14mu} {signal}\mspace{14mu} {configurations}\mspace{14mu} 20\text{-}31},} \\{{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix} \\l^{''} & \begin{matrix}{{{CSI}\mspace{14mu} {reference}\mspace{14mu} {signal}\mspace{14mu} {configurations}\mspace{14mu} 0\text{-}27},} \\{{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix}\end{matrix}\mspace{20mu} w_{l^{''}}} = \left\{ {{{\begin{matrix}1 & {p \in \left\{ {15,17,19,21} \right\}} \\\left( {- 1} \right)^{l^{''}} & {p \in \left\{ {16,18,20,22} \right\}}\end{matrix}\mspace{20mu} l^{''}} = {{0,1\mspace{20mu} m} = 0}},1,\ldots \;,{{N_{RB}^{DL} - {1\mspace{20mu} m^{\prime}}} = {m + \left\lfloor \frac{N_{RB}^{\max,{DL}} - N_{RB}^{DL}}{2} \right\rfloor}}} \right.} \right.}} \right.}}}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

In Equation 12, (k′,l′) (wherein k′ is a subcarrier index within aresource block and l′ indicates an OFDM symbol index within a slot.) andthe condition of n_s is determined depending on a CSI-RS configuration,such as Table 3 or Table 4.

Table 3 illustrates the mapping of (k′,l′) from a CSI-RS configurationin a normal CP.

TABLE 3 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 configuration (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′,l′) n_(s) mod 2 Frame 0 (9, 5) 0 (9, 5) 0 (9, 5) 0 structure 1 (11, 2) 1 (11, 2)  1 (11, 2)  1 type 1 and 2 2 (9, 2) 1 (9, 2) 1 (9, 2) 1 3 (7,2) 1 (7, 2) 1 (7, 2) 1 4 (9, 5) 1 (9, 5) 1 (9, 5) 1 5 (8, 5) 0 (8, 5) 06 (10, 2)  1 (10, 2)  1 7 (8, 2) 1 (8, 2) 1 8 (6, 2) 1 (6, 2) 1 9 (8, 5)1 (8, 5) 1 10 (3, 5) 0 11 (2, 5) 0 12 (5, 2) 1 13 (4, 2) 1 14 (3, 2) 115 (2, 2) 1 16 (1, 2) 1 17 (0, 2) 1 18 (3, 5) 1 19 (2, 5) 1 Frame 20(11, 1)  1 (11, 1)  1 (11, 1)  1 structure 21 (9, 1) 1 (9, 1) 1 (9, 1) 1type 2 only 22 (7, 1) 1 (7, 1) 1 (7, 1) 1 23 (10, 1)  1 (10, 1)  1 24(8, 1) 1 (8, 1) 1 25 (6, 1) 1 (6, 1) 1 26 (5, 1) 1 27 (4, 1) 1 28 (3, 1)1 29 (2, 1) 1 30 (1, 1) 1 31 (0, 1) 1

Table 4 illustrates the mapping of (k′,l′) from a CSI-RS configurationin an extended CP.

TABLE 4 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 configuration (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′,l′) n_(s) mod 2 Frame 0 (11, 4)  0 (11, 4)  0 (11, 4)  0 structure 1 (9,4) 0 (9, 4) 0 (9, 4) 0 type 1 and 2 2 (10, 4)  1 (10, 4)  1 (10, 4)  1 3(9, 4) 1 (9, 4) 1 (9, 4) 1 4 (5, 4) 0 (5, 4) 0 5 (3, 4) 0 (3, 4) 0 6 (4,4) 1 (4, 4) 1 7 (3, 4) 1 (3, 4) 1 8 (8, 4) 0 9 (6, 4) 0 10 (2, 4) 0 11(0, 4) 0 12 (7, 4) 1 13 (6, 4) 1 14 (1, 4) 1 15 (0, 4) 1 Frame 16 (11,1)  1 (11, 1)  1 (11, 1)  1 structure 17 (10, 1)  1 (10, 1)  1 (10, 1) 1 type 2 only 18 (9, 1) 1 (9, 1) 1 (9, 1) 1 19 (5, 1) 1 (5, 1) 1 20(4, 1) 1 (4, 1) 1 21 (3, 1) 1 (3, 1) 1 22 (8, 1) 1 23 (7, 1) 1 24 (6, 1)1 25 (2, 1) 1 26 (1, 1) 1 27 (0, 1) 1

reduce inter-cell interference (ICI) in a multi-cell environmentincluding a heterogeneous network (HetNet) environment, a maximum of 32different configurations (in the case of a normal CP) or a maximum of 28different configurations (in the case of an extended CP) are defined.

The CSI-RS configuration is different depending on the number of antennaports and a CP within a cell, and a neighboring cell may have a maximumof different configurations. Furthermore, the CSI-RS configuration maybe divided into a case where it is applied to both an FDD frame and aTDD frame and a case where it is applied to only a TDD frame dependingon a frame structure.

(k′,l′) and n_s are determined depending on a CSI-RS configuration basedon Table 3 and Table 4, and time-frequency resources used for CSI-RStransmission are determined depending on each CSI-RS antenna port.

FIG. 8 is a diagram illustrating resources to which reference signalsare mapped in a wireless communication system to which the presentinvention may be applied.

FIG. 8(a) shows twenty types of CSI-RS configurations available forCSI-RS transmission by one or two CSI-RS antenna ports, FIG. 8(b) showsten types of CSI-RS configurations available for four CSI-RS antennaports, and FIG. 8(c) shows five types of CSI-RS configurations availablefor eight CSI-RS antenna ports.

As described above, radio resources (i.e., an RE pair) in which a CSI-RSis transmitted are determined depending on each CSI-RS configuration.

If one or two antenna ports are configured for CSI-RS transmission withrespect to a specific cell, the CSI-RS is transmitted on radio resourceson a configured CSI-RS configuration of the twenty types of CSI-RSconfigurations shown in FIG. 8(a).

Likewise, when four antenna ports are configured for CSI-RS transmissionwith respect to a specific cell, a CSI-RS is transmitted on radioresources on a configured CSI-RS configuration of the ten types ofCSI-RS configurations shown in FIG. 8(b). Furthermore, when eightantenna ports are configured for CSI-RS transmission with respect to aspecific cell, a CSI-RS is transmitted on radio resources on aconfigured CSI-RS configuration of the five types of CSI-RSconfigurations shown in FIG. 8(c).

A CSI-RS for each antenna port is subjected to CDM for every two antennaports (i.e., {15,16}, {17,18}, {19,20} and {21,22}) on the same radioresources and transmitted. For example, in the case of antenna ports 15and 16, CSI-RS complex symbols for the respective antenna ports 15 and16 are the same, but are multiplied by different types of orthogonalcode (e.g., Walsh code) and mapped to the same radio resources. Thecomplex symbol of the CSI-RS for the antenna port 15 is multiplied by[1, 1], and the complex symbol of the CSI-RS for the antenna port 16 ismultiplied by [1 −1] and mapped to the same radio resources. The same istrue of the antenna ports {17,18}, {19,20} and {21,22}.

A UE may detect a CSI-RS for a specific antenna port by multiplying codeby which a transmitted symbol has been multiplied. That is, atransmitted symbol is multiplied by the code [1 1] multiplied in orderto detect the CSI-RS for the antenna port 15, and a transmitted symbolis multiplied by the code [1 −1] multiplied in order to detect theCSI-RS for the antenna port 16.

Referring to FIGS. 8(a) to 8(c), in the case of the same CSI-RSconfiguration index, radio resources according to a CSI-RS configurationhaving a large number of antenna ports include radio resources having asmall number of CSI-RS antenna ports. For example, in the case of aCSI-RS configuration 0, radio resources for the number of eight antennaports include both radio resources for the number of four antenna portsand radio resources for the number of one or two antenna ports.

A plurality of CSI-RS configurations may be used in one cell. 0 or oneCSI-RS configuration may be used for a non-zero power (NZP) CSI-RS, and0 or several CSI-RS configurations may be used for a zero power (ZP)CSI-RS.

For each bit set to 1 in a zeropower (ZP) CSI-RS (‘ZeroPowerCSI-RS) thatis a bitmap of 16 bits configured by a high layer, a UE assumes zerotransmission power in REs (except a case where an RE overlaps an REassuming a NZP CSI-RS configured by a high layer) corresponding to thefour CSI-RS columns of Table 3 and Table 4. The most significant bit(MSB) corresponds to the lowest CSI-RS configuration index, and nextbits in the bitmap sequentially correspond to next CSI-RS configurationindices.

A CSI-RS is transmitted only in a downlink slot that satisfies thecondition of (n_s mod 2) in Table 3 and Table 4 and a subframe thatsatisfies the CSI-RS subframe configurations.

In the case of the frame structure type 2 (TDD), a CSI-RS is nottransmitted in a special subframe, a synchronization signal (SS), asubframe colliding against a PBCH or SystemInformationBlockType1 (SIB 1)Message transmission or a subframe configured to paging messagetransmission.

Furthermore, an RE in which a CSI-RS for any antenna port belonging toan antenna port set S (S={15}, S={15,16}, S={17,18}, S={19,20} orS={21,22}) is transmitted is not used for the transmission of a PDSCH orfor the CSI-RS transmission of another antenna port.

Time-frequency resources used for CSI-RS transmission cannot be used fordata transmission. Accordingly, data throughput is reduced as CSI-RSoverhead is increased. By considering this, a CSI-RS is not configuredto be transmitted every subframe, but is configured to be transmitted ineach transmission period corresponding to a plurality of subframes. Inthis case, CSI-RS transmission overhead can be significantly reducedcompared to a case where a CSI-RS is transmitted every subframe.

A subframe period (hereinafter referred to as a “CSI transmissionperiod”) T_CSI-RS and a subframe offset Δ_CSI-RS for CSI-RS transmissionare shown in Table 5.

Table 5 illustrates CSI-RS subframe configurations

TABLE 5 CSI-RS periodicity CSI-RS subframe offset CSI-RS-SubframeConfigT_(CSI-RS) Δ_(CSI-RS) I_(CSI-RS) (subframes) (subframes) 0-4 5I_(CSI-RS)  5-14 10 I_(CSI-RS)-5 15-34 20 I_(CSI-RS)-15 35-74 40I_(CSI-RS)-35  75-154 80 I_(CSI-RS)-75

Referring to Table 5, the CSI-RS transmission period T_CSI-RS and thesubframe offset Δ_CSI-RS are determined depending on the CSI-RS subframeconfiguration I_CSI-RS.

The CSI-RS subframe configuration of Table 5 may be configured as one ofthe aforementioned ‘SubframeConfig’ field and‘zeroTxPowerSubframeConfig’ field. The CSI-RS subframe configuration maybe separately configured with respect to an NZP CSI-RS and a ZP CSI-RS.

A subframe including a CSI-RS satisfies Equation 13.

(10n _(f) +└n _(s)/2┘−Δ_(CSI-RS))mod T _(CSI-RS)=0  [Equation 13]

In Equation 13, T_CSI-RS means a CSI-RS transmission period, Δ_CSI-RSmeans a subframe offset value, n_f means a system frame number, and n_smeans a slot number.

In the case of a UE in which the transmission mode 9 has been configuredwith respect to a serving cell, one CSI-RS resource configuration may beconfigured for the UE. In the case of a UE in which the transmissionmode 10 has been configured with respect to a serving cell, one or moreCSI-RS resource configuration (s) may be configured for the UE.

In the current LTE standard, a CSI-RS configuration includes an antennaport number (antennaPortsCount), a subframe configuration(subframeConfig), and a resource configuration (resourceConfig).Accordingly, the a CSI-RS configuration provides notification that aCSI-RS is transmitted how many antenna port, provides notification ofthe period and offset of a subframe in which a CSI-RS will betransmitted, and provides notification that a CSI-RS is transmitted inwhich RE location (i.e., a frequency and OFDM symbol index) in acorresponding subframe.

Specifically, the following parameters for each CSI-RS (resource)configuration are configured through high layer signaling.

-   -   If the transmission mode 10 has been configured, a CSI-RS        resource configuration identifier    -   A CSI-RS port number (antennaPortsCount): a parameter (e.g., one        CSI-RS port, two CSI-RS ports, four CSI-RS ports or eight CSI-RS        ports) indicative of the number of antenna ports used for CSI-RS        transmission    -   A CSI-RS configuration (resourceConfig) (refer to Table 3 and        Table 4): a parameter regarding a CSI-RS allocation resource        location    -   A CSI-RS subframe configuration (subframeConfig, that is,        I_CSI-RS) (refer to Table 5): a parameter regarding the period        and/or offset of a subframe in which a CSI-RS will be        transmitted    -   If the transmission mode 9 has been configured, transmission        power P_C for CSI feedback: in relation to the assumption of a        UE for reference PDSCH transmission power for feedback, when the        UE derives CSI feedback and takes a value within a [−8, 15] dB        range in a 1-dB step size, P_C is assumed to be the ratio of        energy per resource element (EPRE) per PDSCH RE and a CSI-RS        EPRE.    -   If the transmission mode 10 has been configured, transmission        power P_C for CSI feedback with respect to each CSI process. If        CSI subframe sets C_CSI,0 and C_CSI,1 are configured by a high        layer with respect to a CSI process, P_C is configured for each        CSI subframe set in the CSI process.    -   A pseudo-random sequence generator parameter n_ID    -   If the transmission mode 10 has been configured, a high layer        parameter ‘qcl-CRS-Info-r11’ including a QCL scrambling        identifier for a quasico-located (QCL) type B UE assumption        (qcl-ScramblingIdentity-r11), a CRS port count        (crs-PortsCount-r11), and an MBSFN subframe configuration list        (mbsfn-SubframeConfigList-r11) parameter.

When a CSI feedback value derived by a UE has a value within the [−8,15] dB range, P_C is assumed to be the ration of PDSCH EPRE to CSI-RSEPRE. In this case, the PDSCH EPRE corresponds to a symbol in which theratio of PDSCH EPRE to CRS EPRE is ρ_A.

A CSI-RS and a PMCH are not configured in the same subframe of a servingcell at the same time.

In the frame structure type 2, if four CRS antenna ports have beenconfigured, a CSI-RS configuration index belonging to the [20-31] set(refer to Table 3) in the case of a normal CP or a CSI-RS configurationindex belonging to the [16-27] set (refer to Table 4) in the case of anextended CP is not configured in a UE.

A UE may assume that the CSI-RS antenna port of a CSI-RS resourceconfiguration has a QCL relation with delay spread, Doppler spread,Doppler shift, an average gain and average delay.

A UE in which the transmission mode 10 and the QCL type B have beenconfigured may assume that antenna ports 0-3 corresponding to a CSI-RSresource configuration and antenna ports 15-22 corresponding to a CSI-RSresource configuration have QCL relation with Doppler spread and Dopplershift.

In the case of a UE in which the transmission modes 1-9 have beenconfigured, one ZP CSI-RS resource configuration may be configured inthe UE with respect to a serving cell. In the case of a UE in which thetransmission mode 10 has been configured, one or more ZP CSI-RS resourceconfigurations may be configured in the UE with respect to a servingcell.

The following parameters for a ZP CSI-RS resource configuration may beconfigured through high layer signaling.

-   -   The ZP CSI-RS configuration list (zeroTxPowerResourceConfigList)        (refer to Table 3 and Table 4): a parameter regarding a        zero-power CSI-RS configuration    -   The ZP CSI-RS subframe configuration (eroTxPowerSubframeConfig,        that is, I_CSI-RS) (refer to Table 5): a parameter regarding the        period and/or offset of a subframe in which a zero-power CSI-RS        is transmitted

A ZP CSI-RS and a PMCH are not configured in the same subframe of aserving cell at the same time.

In the case of a UE in which the transmission mode 10 has beenconfigured, one or more channel state information-interferencemeasurement (CSI-IM) resource configurations may be configured in the UEwith respect to a serving cell.

The following parameters for each CSI-IM resource configuration may beconfigured through high layer signaling.

-   -   The ZP CSI-RS configuration (refer to Table 3 and Table 4)    -   The ZP CSI RS subframe configuration I_CSI-RS (refer to Table 5)

A CSI-IM resource configuration is the same as any one of configured ZPCSI-RS resource configurations.

A CSI-IM resource and a PMCH are not configured within the same subframeof a serving cell at the same time.

Sounding Reference Signal (SRS)

An SRS is mainly used for channel quality measurement to perform uplinkfrequency-selective scheduling and is not related to transmission ofuplink data and/or control information. However, the present inventionis not limited thereto and the SRS may be used for various otherpurposes to enhance power control or to support various start-upfunctions of recently unscheduled terminals. As an example of thestart-up function, an initial modulation and coding scheme (MCS),initial power control for data transmission, timing advance, andfrequency semi-selective scheduling may be included. In this case,frequency semi-selective scheduling refers to scheduling thatselectively allocates frequency resources to a first slot of a subframeand allocating the frequency resources by pseudo-randomly jumping toanother frequency in a second slot.

Further, the SRS may be used for measuring a downlink channel qualityunder the assumption that radio channels are reciprocal between theuplink and the downlink. The assumption is particularly effective in atime division duplex (TDD) system in which the uplink and the downlinkshare the same frequency spectrum and are separated in a time domain.

The SRS subframes transmitted by a certain UE in a cell may berepresented by a cell-specific broadcast signal. A 4 bit cell-specific‘srsSubframeConfiguration’ parameter represents 15 available subframearrays through which the SRS may be transmitted over each radio frame.The arrays provide flexibility for adjustment of SRS overhead accordingto a deployment scenario.

A 16-th array completely turns off a switch of the SRS in the cell andthis is primarily suitable for a serving cell that serves high-speedterminals.

FIG. 9 illustrates an uplink subframe including a sounding referencesignal symbol in a wireless communication system to which the presentinvention may be applied.

Referring to FIG. 9, the SRS is continuously transmitted on the lastSC-FDMA symbol on the arranged subframe. Therefore, the SRS and the DMRSare located in different SC-FDMA symbols.

PUSCH data transmission is not allowed in a specific SC-FDMA symbol forSRS transmission and as a result, when the sounding overhead is thehighest, that is, even if SRS symbols are included in all subframes, thesounding overhead does not exceed approximately 7%.

Each SRS symbol is generated by a basic sequence (random sequence or asequence set based on Zadoff-Ch (ZC)) for a given time unit andfrequency band, and all terminals in the same cell use the same basicsequence. In this case, the SRS transmissions from a plurality of UEs inthe same cell at the same time in the same frequency band are orthogonalby different cyclic shifts of the basic sequence, and are distinguishedfrom each other.

By assigning different basic sequences to respective cells, the SRSsequences from different cells may be distinguished, but orthogonalitybetween different basic sequences is not guaranteed.

As more and more communication devices require larger communicationcapacity, there is a need for improved mobile broadband communicationcompared to the existing radio access technology (RAT). Massive machinetype communications (MTCs), which provide various services anytime andanywhere by connecting many devices and objects, are one of the majorissues to be considered in the next generation communication. Inaddition, a communication system design considering a service/UEsensitive to reliability and latency is being discussed.

The introduction of next generation radio access technology consideringenhanced mobile broadband communication, massive MTC, ultra-reliable andlow latency communication (URLLC) is discussed, and in the presentinvention, the technology is called new RAT for convenience.

Self-Contained Subframe Structure

FIG. 10 is a diagram illustrating a self-contained subframe structure inthe wireless communication system to which the present invention may beapplied.

In a TDD system, in order to minimize the latency of data transmission,a 5 generation (5G) new RAT considers a self-contained subframestructure as shown in FIG. 10.

In FIG. 10, a dashed area (symbol index of 0) indicates a downlink (DL)control area and a black area (symbol index of 13) indicates an uplink(UL) control area. An unmarked area may also be used for DL datatransmission or for UL data transmission. Such a structure ischaracterized in that DL transmission and UL transmission aresequentially performed in one subframe, and DL data is transmitted in asubframe, and UL ACK/NACK may also be received. As a result, it takesless time to retransmit data when a data transmission error occurs,thereby minimizing the latency of final data transmission.

In such a self-contained subframe structure, there is a need for a timegap between the base station and the UE for the conversion process fromthe transmission mode to the reception mode or from the reception modeto the transmission mode. For this end, some OFDM symbols at the time ofswitching from DL to UL in the self-contained subframe structure areconfigured to a guard period (GP).

Analog Beamforming

In a millimeter wave (mmW), a wavelength is shortened, so that aplurality of antenna elements may be installed in the same area. Thatis, a total of 64 (8×8) antenna elements may be installed in a2-dimension array at a 0.5 lambda (that is, wavelength) interval on apanel of 4×4 (4 by 4) cm with a wavelength of 1 cm in a 30 GHz band.Therefore, in the mmW, it is possible to increase a beamforming (BF)gain to increase coverage or increase throughput by using multipleantenna elements.

In this case, if a transceiver unit (TXRU) is provided so thattransmission power and phase may be adjusted for each antenna element,independent beamforming is possible for each frequency resource.However, when the TXRUs are installed on all 100 antenna elements, thereis a problem that effectiveness is deteriorated in terms of costs.Therefore, a method of mapping a plurality of antenna elements to oneTXRU and adjusting a direction of a beam using an analog phase shifteris considered. Such an analog BF method has a disadvantage in thatfrequency selective BF may not be performed by making only one beamdirection in all bands.

A hybrid BF with B TXRUs, which is an intermediate form of digital BFand analog BF, and fewer than Q antenna elements, may be considered. Inthis case, although there is a difference depending on a connectionmethod of B TXRUs and Q antenna elements, the number of directions ofthe beams that may be transmitted at the same time is limited to B orless.

Hereinafter, representative examples of a method of connection method ofTXRUs and antenna elements will be described with reference to theaccompanying drawing.

FIG. 11 shows a transceiver unit model in a radio communication systemto which the present invention may be applied.

A TXRU virtualization model shows a relationship between an outputsignal of the TXRUs and an output signal of the antenna elements.According to the correlation between the antenna element and the TXRU,The TXRU virtualization model may be divided into TXRU virtualizationmodel option-1 and a sub-array partition model as illustrated in FIG.11(a) and TXRU virtualization model option-2 and a full-connection modelas illustrated in FIG. 11 (b).

Referring to FIG. 11(a), in the case of the sub-array partition model,the antenna element is divided into multiple antenna element groups andeach TXRU is connected to one of the groups. In this case, the antennaelement is connected to only one TXRU.

Referring to FIG. 11(b), in the case of the full-connection model,signals of multiple TXRUs are combined and transmitted to a singleantenna element (or an array of antenna elements). That is, a scheme isillustrated, in which the TXRU is connected to all antenna elements. Inthis case, the antenna element is connected to all TXRUs.

In FIG. 11, q represents a transmission signal vector of antennaelements having M co-polarized waves in one column. w represents awideband TXRU virtualization weight vector and W represents a phasevector multiplied by an analog phase shifter. In other words, thedirection of analog beamforming is determined by W. x represents asignal vector of M_TXRU TXRUs.

Herein, mapping of the antenna ports and the TXRUs may be 1-to-1 or1-to-many.

In FIG. 11, the mapping (TXRU-to-element mapping) between the TXRU andthe antenna element is merely an example, and the present invention isnot limited thereto. The present invention may be similarly applied evento mapping between the TXRU and the antenna element, which may beimplemented in various other forms in terms of hardware.

Feedback of Channel State Information (CSI)

In a 3GPP LTE/LTE-A system, user equipment (UE) is defined to reportchannel state information (CSI) to a base station (BS or eNB).

The CSI collectively refers to information that may indicate the qualityof a radio channel (or referred to as a link) formed between the UE andthe antenna port. For example, a rank indicator (RI), a precoding matrixindicator (PMI), a channel quality indicator (CQI), and the likecorrespond to the information.

Here, the RI represents rank information of a channel, which means thenumber of streams received by the UE through the same time-frequencyresource. Since this value is determined depending on the long termfading of the channel, the value is fed back from the UE to the BS witha period usually longer than the PMI and the CQI. The PMI is a valuereflecting a channel space characteristic and represents a preferredprecoding index preferred by the UE based on a metric such assignal-to-interference-plus-noise ratio (SINR). The CQI is a valuerepresenting the strength of the channel, and generally refers to areception SINR that may be obtained when the BS uses the PMI.

In the 3GPP LTE/LTE-A system, the BS configures a plurality of CSIprocesses to the UE and may receive CSI for each process. Here, the CSIprocess is constituted by a CSI-RS for signal quality measurement fromthe BS and a CSI-interference measurement (CSI-IM) resource forinterference measurement.

Reference Signal (RS) Virtualization

In the mmW, it is possible to transmit a PDSCH only in one analog beamdirection at a time by analog beamforming. In this case, datatransmission from the BS is possible only to a small number of UEs inthe corresponding direction. Therefore, if necessary, the analog beamdirection is differently configured for each antenna port so that datatransmission may be simultaneously performed to a plurality of UEs inseveral analog beam directions.

FIG. 12 is a diagram illustrating a service area for each transceiverunit in the wireless communication system to which the present inventionmay be applied.

In FIG. 12, 256 antenna elements are divided into 4 parts to form a 4sub-arrays, and the structure of connecting the TXRU to the sub-arraywill be described as an example as shown in FIG. 11 above.

When each sub-array is constituted by a total of 64 (8×8) antennaelements in the form of a 2-dimensional array, specific analogbeamforming may cover an area corresponding to a 15-degree horizontalangle area and a 15-degree vertical angle area. That is, the zone wherethe BS should be served is divided into a plurality of areas, andservices are provided one by one at a time.

In the following description, it is assumed that the CSI-RS antennaports and the TXRUs are 1-to-1 mapped. Therefore, the antenna port andthe TXRU have the same meaning as the following description.

As shown in FIG. 12(a), if all TXRUs (antenna ports, sub-arrays) (thatis, TXRU 0, 1, 2, 3) have the same analog beamforming direction (thatis, region 1), the throughput of the corresponding zone may be increasedby forming digital beam with higher resolution. Also, it is possible toincrease the throughput of the corresponding zone by increasing the rankof the transmission data to the corresponding zone.

As shown in FIGS. 12(b) and 12(c), if each TXRU (antenna port,sub-array) (that is, TXRU 0, 1, 2, 3) has a different analog beamformingdirection (that is, region 1 or region 2, the data may be transmittedsimultaneously to UEs distributed in a wider area in the subframe (SF).

As an example shown in FIGS. 12(b) and 12(c), two of the four antennaports are used for PDSCH transmission to UE1 in region 1 and theremaining two antenna ports are used for PDSCH transmission to UE2 inregion 2.

Particularly, in FIG. 12(b), PDSCH1 transmitted to UE1 and PDSCH2transmitted to UE2 represent examples of spatial division multiplexing(SDM). Unlike this, as shown in FIG. 12(c), PDSCH1 transmitted to UE1and PDSCH2 transmitted to UE2 may also be transmitted by frequencydivision multiplexing (FDM).

Among a scheme of serving one area using all the antenna ports and ascheme of serving many areas at the same time by dividing the antennaports, a preferred scheme is changed according to the rank and themodulation and coding scheme (MCS) servicing to the UE for maximizingthe cell throughput. Also, the preferred method is changed according tothe amount of data to be transmitted to each UE.

The BS calculates a cell throughput or scheduling metric which may beobtained when one area is served using all the antenna ports, andcalculates the cell throughput or scheduling metric which may beobtained when two areas are served by dividing the antenna ports. The BScompares the cell throughput or the scheduling metric which may beobtained by each scheme to select the final transmission scheme. As aresult, the number of antenna ports participating in PDSCH transmissionis changed by SF-by-SF. In order for the BS to calculate thetransmission MCS of the PDSCH according to the number of antenna portsand reflect the calculated transmission MCS to a scheduling algorithm,the CSI feedback from the appropriate UE is required.

Beam Reference Signal (BRS)

Beam reference signals are transmitted on one or more antenna ports(p={0, 1, . . . , 7}).

The reference-signal sequence ‘r_l(m)’ may be defined by Equation 14below.

$\begin{matrix}{{{r_{l}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \;,{{8 \cdot \left( {N_{RB}^{\max,{DL}} - 18} \right)} - 1}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Where l=0, 1, . . . , 13 is the OFDM symbol number. N_RB^(∧)max,DLrepresents the largest downlink band configuration and N_sc^(∧)RB isexpressed by a multiple. N_sc^(∧)RB represents the size of the resourceblock in the frequency domain and is expressed by the number ofsubcarriers.

In Equation 14, c(i) may be predefined as a pseudo-random sequence. Thepseudo-random sequence generator may be initialized at the start of eachOFDM symbol by using Equation 15 below.

C _(init)=2¹⁰·(7·(n _(s)+1)+l′+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID)^(cell)+1  [Equation 15]

Where N_ID^(∧)cell represents a physical layer cell identifier.n_s=floor(l/7) and floor(x) represents a floor function for deriving amaximum integer of x or less. l′=l mod 7 and mod represents a modulooperation.

Beam Refinement Reference Signal (BRRS)

Beam refinement reference signals (BRRSs) may be transmitted on up toeight antenna ports (p=600, . . . , 607). The transmission and receptionof the BRRS are dynamically scheduled in the downlink resourceallocation on xPDCCH.

The reference-signal sequence ‘r_l,ns(m)’ may be defined by Equation 16below.

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \;,{\left\lfloor {\frac{3}{8}N_{RB}^{\max,{DL}}} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

Where n_s represents the slot number in the radio frame. l representsthe OFDM symbol number in the slot. c(i) may be predefined as thepseudo-random sequence. The pseudo-random sequence generator may beinitialized at the start of each OFDM symbol by using Equation 17 below.

c _(init)=2¹⁰(7( n _(s)+1)+l+1)(2N _(ID) ^(BRRS)+1)+2N _(ID)^(BRRS)+1  [Equation 17]

-   -   n _(s)=n_(s) mod 20

Herein, N_ID^(∧)BRRS is configured to the UE through the RRC signaling.

DL Phase Noise Compensation Reference Signal

Phase noise compensation reference signals associated with xPDSCH may betransmitted on antenna port(s) p=60 and/or p=61 according to thesignaling in the DCI. Further, the phase noise compensation referencesignals associated with xPDSCH may be present as a valid reference forphase noise compensation only if the xPDSCH transmission is associatedwith the corresponding antenna port. In addition, the phase noisecompensation reference signals associated with xPDSCH may be transmittedonly on the physical resource blocks and symbols upon which thecorresponding xPDSCH is mapped. Moreover, the phase noise compensationreference signals associated with xPDSCH may be identical in all symbolswith xPDSCH allocation.

For any antenna port p∈{60,61}, the reference-signal sequence ‘r(m)’ isdefined by Equation 18 below.

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \;,{\left\lfloor {N_{RB}^{\max,{DL}}\text{/}4} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 18} \right\rbrack\end{matrix}$

Herein, c(i) may be predefined as the pseudo-random sequence. Thepseudo-random sequence generator may be initialized at the start of eachsubframe by using Equation 19 below.

c _(init)(└n _(s)/2┘+1)·(2n _(ID) ^((n) ^(SCID) ⁾+1)·2¹⁶ +n_(SCID)  [Equation 19]

Where n_SCID is 0 if unless specified otherwise. In the xPDSCHtransmission, n_SCID is given in a DCI format associated with the xPDSCHtransmission.

n_ID_(∧)(i) (where i=0, 1) is given as follows. When the value ofn_ID^(∧)PCRS,i is not provided by the higher layer, n_ID^(∧)(i) is equalto N_ID^(∧)cell. If not, n_ID_(∧)(i) is equal to n_ID^(∧)PCRS,i.

According to the conference of 3GPP RAN1 #86, DL Layer 1 (L1)/Layer (L2)beam management procedures are supported within the following one ormultiple transmission reception points (TRPs).

i) P-1: P-1 is used to enable UE measurements on different TRP Tx beamsto support selection of TRP transmission (Tx) beam(s)/UE reception (Rx)beam(s).

-   -   For beamforming in the TRP, P-1 includes intra-TRP/inter-TRP Tx        beam sweeps from a set of different beams.    -   For beamforming in the UE, P-1 includes UE Rx beam sweeps from a        set of different beams.    -   The TRP Tx beam and the UE Rx beam may be jointly or        individually determined.

ii) P-2: P-2 is used to enable UE measurements on different TRP Tx beamsso as to change inter/intra-TRP Tx beam(s).

-   -   A smaller set of beams for beam refinement than in P-1 may be        used.    -   P-2 may be regarded as a special case of P-1.

iii) P-3: P-3 is used to enable UE measurement on the same TRP Tx beamto change UE Rx beam in the case where the UE uses beamforming.

-   -   The same procedure may be designed for intra-TRP beam        measurement and inter-TRP beam measurement.    -   The UE may not know the intra-TRP beam or the inter-TRP beam.

For example, procedures P-2 and P-3 described above may be performedjointly and/or multiple times to achieve TRP Tx/UE Rx beam changesimultaneously.

Managing multiple Tx/Rx beam pairs may be supported for a single UE.

Assistance information from another carrier is being discussed to betransferred to the UE in a beam management procedure.

The above procedure can be applied to any frequency band.

The above procedure can be used in single/multiple beam(s) per TRP.

Further, according to the conference of 3GPP RAN1 #86bis, the followingUL beam management is to be further studied in NR.

-   -   A procedure similar to downlink beam management may be defined.

i) U-1: U-1 is used to enable TRP measurements on different UE Tx beamsin order to support selection of the UE Tx beam(s)/TRP Rx beam(s).

-   -   This may not necessarily be used in all cases.

ii) U-2: U-2 is used to enable TRP measurements on different TRP Rxbeams so as to change/select the inter/intra-TRP Rx beam(s).

iii) U-3: U-3 is used to enable TRP measurement on the same TRP Rx beamto change UE Tx beam in the case where the UE uses beamforming.

Indication of information related to Tx/Rx correspondence may besupported.

UL beam management is studied based on: Physical Random Access Channel(PRACH), Sounding Reference Signal (SRS), and Demodulation ReferenceSignal (DM-RS) (Other channels and reference signals (RS) are notprecluded.).

As described below, the uplink (UL) beam management procedure needs tobe studied by considering the Tx/Rx beam correspondence.

-   -   For the case where both the TRP and the UE have the Tx/Rx beam        correspondence    -   For the case where the TRP does not have the Tx/Rx beam        correspondence and/or the UE does not have the Tx/Rx beam        correspondence

Further, the following aspects should be considered for UL power control(PC) design:

-   -   No LTE-like cell-specific reference signal for path loss        estimate    -   Beam-based transmissions/receptions    -   Analog beamforming at eNB/UE    -   Multi-beam/multi-stream transmissions    -   Multiple numerologies    -   Inter-TRP information exchange    -   Dynamic TDD may be studied afterwards and other aspects are not        precluded.

Further, the following design of UL PC is studied as a starting point:

-   -   Fractional power control in LTE as framework    -   DL RS for path loss measurement, e.g., RS in DL beam management        P-1, P-2 and P-3 for multi-beam scenario or single-beam scenario    -   Separate PC settings for UL control and data channel

For UL PC, numerology-specific parameter setting and separate PCsettings for multi-beam/multi-stream UL may be studied afterwards.

Further, according to the conference of 3GPP RAN1 #87, in the NR, forNR-PUSCH in at least targeting enhanced mobile broadband (eMBB),

-   -   Open-loop power control based on pathloss estimate is supported.        In this case, pathloss is estimated using DL RS for measurement.        Further, fractional power control is supported. For which        measurement DL RS(s) is used (The RS may be beamformed) may be        studied afterwards.    -   Closed-loop power control is supported, which is based on NW        signaling. In this case, dynamic UL-power adjustment is        considered.

The followings may be additionally studied:

-   -   Numerology specific power control, e.g., numerology specific        power control parameters    -   Beam specific power control parameters    -   Power control for other RSs and physical channels    -   Power control for grant free PUSCH if supported    -   Power control per layer (group)

Further, in the NR, the CSI-RS supports DL Tx beam sweeping and UE Rxbeam sweeping. In this case, the CSI-RS may be used in P-1, P-2, andP-3.

The NR CSI-RS supports the following mapping structure.

-   -   N_P CSI-RS port(s) may be mapped for each (sub) time unit.    -   Throughout the (sub) time unit, the same CSI-RS antenna ports        may be mapped.    -   A value of N_P is studied afterwards.    -   Here, “time unit” means n (>=1) OFDM symbols in        configured/reference numerology. Whether consecutive or        inconsecutive OFDM symbols comprising the time unit is studied        afterwards.    -   Port multiplexing method (e.g., FDM, TDM, CDM, any combinations)        is studied afterwards.    -   Each time unit may be divided into sub-time units.    -   Partitioning method (e.g., TDM, interleaved FDMA (IFDMA), OFDM        symbol-level partition with same/shorter OFDM symbol length        (i.e. larger subcarrier spacing) as/than the reference OFDM        symbol length (subcarrier spacing), and other methods are not        precluded) is studied afterwards.    -   Such a mapping structure may be used to support multiple        panels/Tx chains.    -   CSI-RS mapping options for Tx and Rx beam sweeping are described        below.

i) Option 1: Tx beam(s) are the same across sub-time units within eachtime unit. Tx beam(s) are different across time units.

ii) Option 2: Tx beam(s) are different across sub-time units within eachtime unit. Tx beam(s) are the same across the time units.

iii) Combination of Option 1 and Option 2:

The Tx beam(s) are the same across the sub-time units within one timeunit.

The Tx beam(s) are different for each sub-time unit within another timeunit.

Here, for example, a combination of the different time units in terms ofe.g., number and periodicity is studied afterwards.

Only Tx sweeping or Rx sweeping may be possible and another option isalso not precluded.

Whether the above mapping structure is configured with one or multipleCSI-RS resources is studied afterwards.

Uplink Transmission/Reception Method

A name of the eNB described in the patent is used as a comprehensiveterm including remote radio head (RRH), eNB (or gNB), transmission point(TP), reception point (RP), a relay, and the like. Hereinafter, forconvenience of description, a proposal method will be described based ona 3GPP LTE system and/or a new RAT (NR) system. However, a range of thesystem to which the proposal method is applied may be extended to othersystems (e.g., UTRA, and the like) other than the 3GPP LTE system.

Hereinafter, a UL transmission power control method in the NR will bedescribed.

In NR system design, it is being considered to introduce new features inUL such as OFDM based UL transmission and single symbol UL controlchannel. The present invention proposes a method in which a UL powercontrol procedure should be considered, which includes basic componentssuch as pathloss compensation, power offset, Transmit Power Control(TPC) command, and some additional feature.

Basic Parameters for the UL Power Control

1-1) Pathloss Compensation

According to UL power control in current LTE system, two types ofpathloss compensation are considered; one is full pathloss compensation,and the other is fractional pathloss compensation.

In NR system, it might be considered that UE measures reference signalreceived power (RSRP) by using a certain type of DL RS (e.g.,synchronization signal, CSI-RS, etc.), and then the UE derives pathlossbetween the UE and its associated eNB by using the measured (high-layerfiltered) RSRP.

UL transmission power from UE may be compensated fully or partially byconsidering the estimated pathloss.

First of all, full pathloss compensation may maximize fairness forcell-edge UEs. In other words, the power received from cell-edge UE atthe gNB (i.e., base station) may be comparable with the power receivedfrom cell-center UE.

On the other hand, if fractional pathloss compensation is used, thereceived power at gNB side from cell-center UE may be much higher thanthat from cell-edge UE. The pathloss of cell-edge UE may be compensatedby adjusting other power parameter or offset so that the received powerfrom cell-edge UE may be properly controlled. However, the receivedpower from cell-center UE may be redundant due to the already sufficientamount of received power in general.

In case of UL data channel transmission, such redundant power can beused to improve spectral efficiency by applying higher Modulation andCoding Scheme (MCS) level (for instance, cell-center UE may be able touse smaller number of PRBs for same TB size). On the other hand, in caseof UL control channel transmission using fixed amount of resources, itis unclear how to use the redundant power to improve spectral efficiencysince a Uplink Control Information (UCI) (payload) size is not dependentupon UE location or channel condition. Hence, it is not desirable toconsider full compensation for the power control of the UL controlchannel.

Furthermore, in case of fractional pathloss compensation for UL datachannel transmission, the received power difference between thecell-center UE and the cell-edge UE may be adjusted by using a value ofa fractional pathloss compensation factor, and this value may bedifferent according to a cell radius and target performance.

Therefore, for the power control of the UL control channel (e.g., PUCCH,etc.), it is desirable to consider the full pathloss compensation.

1-2) Power Offset Depending on Data Rate

In general, it is expected that higher transmission power is required tosupport higher data rate. However, it may be inefficient for the powercontrol of the UL data channel to use both fractional pathlosscompensation and power offset (i.e., Delta_TF setting in the LTEstandard) depending on the data rate simultaneously. Moreover, incurrent LTE, this type of power offset is not supported for higher rankthan 2. Therefore, it needs to be considered to support only thefractional pathloss compensation in the NR without power offset settingdepending on the data rate.

For the power control of the UL data channel, it needs to be consideredto support only the fractional pathloss compensation in the NR withoutthe power offset setting depending on the data rate.

1-3) TPC Command

The TPC command may be used to compensate channel variations due to fastfading. Regarding current LTE, PUCCH power may be adjusted by the TPCcommand signaled in DL assignment DCI while PUSCH (or SRS) power may beadjusted by the TPC command signaled in UL grant DCI. Besides, for theUL transmissions without associated DCI such as semi-persistentscheduling (SPS), periodic CSI, or SRS, the TPC command may be signaledto a certain UE group by using DCI format 3/3A. There may be two typesof TPC procedures for the update of UL transmission power; one isaccumulative TPC, and the other is absolute TPC. The accumulative TPC issuitable for fine-tuning of UE transmission power by using relativelysmall step size of TPC values. On the other hand, the absolute TPC maybe useful to boost the UE transmission power at once by using relativelylarge step size of TPC values.

W the aspects of pathloss compensation are investigated, it is desirableto consider aspects of the pathloss, the power offset, and the TPCcommand for the design of the UL power control procedure for the NR,with consideration of cell deployment, a UL physical channel type (e.g.control or data), and a wireless channel condition.

Additional Features for Power Control in NR

1-4) Beamforming Operation

In the NR design, it may be necessary to consider introduction of analog(or hybrid) beamforming based operation, especially for high frequencyband (e.g. above 6 GHz). With the analog beamforming, gNB TX/RX beamsweeping (e.g. TDM between different gNB TX/RX beams) may be required tobe done not only for the transmission of DL common signal andinformation such as synchronization signal (e.g. PSS/SSS in LTE) orbroadcast system information (e.g. Physical Broadcast Channel (PBCH) inLTE) but also for the transmission of DL/UL control and data channels,in order to serve the UEs located in different areas (or beamdirections).

In this case, it may be necessary to consider differentiation of powercontrol parameters between different beams for the UE since the requiredpower for UL performance is different per beam for the UE.

However, especially for accumulative TPC procedures, it needs to befurther studied whether PC parameter separation per beam is superiorcompared with a common TPC accumulation process regardless of beamchanges or switching. The latter means that the TPC accumulation processwill not be reset even though a serving beam is changed by a beammanagement procedure, considering that the already stabilized transmitpower level is desired to remain as much as possible unless such beamchanges occur to a different TRP.

For targeted service (e.g., Ultra-Reliable and Low-Latency (URLLC) andenhanced Vehicle-to-Everything (eV2X) requiring higher reliability,there may be a configurable additional power offset to be applied on theTPC accumulation process whenever beam change or switching occurs withinthe same TRP so as to alleviate potential power control mismatch due tothe beam change/switching. Further, this may be applied forretransmission cases to improve HARQ performance, which needs to be donefollowing higher-layer configurations provided by the gNB.

For accumulative TPC procedures, a configurable additional power offsetto be applied on a common TPC accumulation process needs to beconsidered, whenever beam change or switching occurs within the sameTRP, depending on a targeted service (e.g., URLLC and eV2X) requiringhigher reliability.

In this regard, when the proposal of the present invention will bedescribed in more detail, the following issues need to be considered inrelation to “Beam specific power control parameters” in the UL PCrelated contents of the above-mentioned 3GPP RAN1 #87 conference.

-   -   An issue should be considered, in which how transmit power        control (TPC) is performed (when the UE transmits UL) while a        reception point (e.g., the eNB) targeted by a transmission        signal is the same (by specific beam management), when an Rx        beam of the reception point is changed (and/or when the Tx beam        of a transmitter (e.g., the eNB) is changed).

As a solution for the issue, in one method, TPCchain/process/parameter(s) for each specific beam may be independentlyconfigured. As a result, independent power control for each beam may beapplied. The reason is that when a transmission/reception beam directionis changed, a best transmission power level may be changed due to achange in reception interference environment, etc.

However, independently performing the power control may not continuouslyguarantee a best operation. Since the reception point itself is notchanged but only a Tx/Rx beam applied to the same transmission/receptionpoint is changed, it may be more advantageous to maintain a PC which ismaintained (stabilized) in the related art, such as TPC accumulation,etc. as possible in terms of performance than application of a rapid TPCchange.

However, since best power control according to beam change/switching maybe slightly changed, at least one technique among techniques proposedbelow may be applied to increase reliability by considering the slightchange of the best power control.

-   -   As described above, a TPC process depending on the beam        change/switching is not initialized with respect to the same        TRP.

In this case, as an example of a method that allows the UE to recognizethe same TRP, “case where beam change/switching occurs based on CSI-RSconfigured in form of (sub-) time unit” may become a condition. That is,when the condition of “case where beam change/switching occurs based onCSI-RS configured in form of (sub-) time unit” is satisfied, the sameTRP may be recognized. For example, the corresponding RS is configuredfor a specific beam management purpose and/or in a single CSI-RSresource configuration or a plurality of CSI-RS configurations, but aspecific group among the plurality of CSI-RS configurations isconfigured (i.e., the same TRP characteristic is configured to be known,etc.), that is, the same TRP may be implicitly (or explicitly)recognized.

For example, under a condition in which a specific group of thecorresponding DL RS (e.g., CSI-RS)/SS(s) “which does not initialize theTPC process (i.e., shares TPC accumulation and/or follows the same UL PCprocess)” is implicitly configured, a rule may be defined/configured,which is determined so that RS/SS(s) which similarly receives the sameTx power value and/or the open-loop P0 value become the same group. Inaddition, in the case of the beam change/switching in the group, the TPCaccumulation may be inherited/shared (e.g., may be the same UL PCprocess).

In this case, in the case of an explicit indication, specific QuasiCo-Located (QCL) signaling capable of identifying the same TRP, etc. maybe explicitly indicated to the UE. For example, specific explicitconfiguration/signaling is provided to allow the specific RS/SS(s) forthe purpose to become the same group, and as a result, the TPCaccumulation may be inherited/shared in the case of the beamchange/switching in the group (e.g., may be the same UL PC process).

Additionally, when the beam change/switching occurs in the same TRP, aspecific power offset value (e.g., P_offset_beam) to be added to a powercontrol process may be RRC-configured (and/or a second layer (L2) levelconfiguration such as a medium access control (MAC) control element(CE), etc. and/or a first layer (layer 1) level configuration such asDCI, etc.) (at one time). That is, in the case of the TPC accumulation,when the beam change/switching occurs, the power offset value (e.g.,P_offset_beam) may be added to a current power value. This is toincrease the reliability.

The power offset value may be RRC-configured (and/or an L2 levelconfiguration such as MAC CE, etc. and/or an L1 level configuration suchas DCI, etc.) differently/independently for each specific service (e.g.,V2X, URLLC, eMBB, . . . , or a specific L1 parameter which maycorrespond to each service, e.g., for each radio network temporaryidentifier (RNTI)).

In The parts described in the above description with the expression“beam change/switching”, the operations of “beam change” and “beamswitching” may be particularly distinguished.

For example, the beam change may mean that only a single serving beam isconfigured and a serving beam is changed. In addition, the beamswitching may mean a case where multiple serving beams are configuredand dynamic beam switching is performed. For example, beam cycling based((semi-) OL transmission) defined/configured by a specific (time-domain)pattern.

In the case of the beam change, how a beam change command is to bedelivered to the UE should be preferentially considered. Morespecifically, if the beam change command is delivered to an L1 signal(e.g., a DCI) or an L2 signal (e.g., a MAC CE), the power offset valueof a large range/high resolution within the message may be delivered.

In addition, a beam switching command may also be delivered to the UEwith the L1 signal (e.g., DCI) or the L2 signal (e.g., MAC CE). The(separate) specific power offset value(s) within the message isdelivered to implicitly or explicitly indicate even informationindicating when the specific power offset value is to be applied. Forexample, when switching periodicity related information of beamswitching/cycling is together configured or separately configured, thepower offset value(s) may be configured to be applied whenever specificbeam switching occurs. For example, a pattern switched after the samebeam is transmitted twice may be configured as an operation of applyingthe power offset value only in first transmission which is switched andtransmitted and not applying the power offset value in secondtransmission.

In addition/alternatively, an indication whether to inherit a previousTPC accumulation value or to reset the previous TPC accumulation valueat the time of delivering the beam change command (and/or beam switchingcommand) may also be together delivered to the UE. For example, theindication may be included in a corresponding L1 and/or L2 commandmessage.

When the previous TPC accumulation value is indicated to be inheritedfrom the eNB, a TPC value (e.g., +X dB, 0 dB, or −Y dB, . . . )indicated in a specific closed-loop TPC field (transmitted together) maybe accumulated and applied to a current TPC accumulation value (further,the power offset value may be additionally summed here (either once orevery time the beam is changed in the case of the beam switching)).

When the previous TPC accumulation value is indicated to be reset fromthe eNB, a TPC value (e.g., +X dB, 0 dB, or −Y dB, . . . ) indicated ina specific closed-loop TPC field (transmitted together) may be appliedas an initial TPC accumulation value on a newly initialized (reset) PCprocess (e.g., an OLPC component may be calculated and thereafter, newlyapplied here as an initial TPC accumulation value) (further, the poweroffset value may be additionally summed here (either once or every timethe beam is changed in the case of the beam switching)).

Further, transmission of the SRS may be required for close-loop PC andin this case, a relationship between an SRS transmission time and abeam/change/switching command deliver time also needs to be definitelyprescribed. For example, when the beam change (or switching) isperformed from beam 1 to beam 2, SRS for a direction of beam 2 may begenerally transmitted after the beam change, but an operation isdefined/configured so as to transmit for a direction of beam 2 beforethe beam change, and as a result, more accurate PC may be performed. Tothis end, with which beam the UE is allowed to transmit the SRS inaperiodic SRS triggering (e.g., via an L1 message) may be explicitlyindicted to the UE. Alternatively, an operation may be configured, toperform a plurality of SRS transmission at a time for a specificpredefined “SRS beam set” which configured in advance (separately). Forexample, in a situation where candidate beams that may be a subject towhich the SRS transmission are defined/configured as beam 1, beam 2, . .. , beam 4, the “SRS beam set” may include all of four beams and forexample, may be configured to include only beam 2 and beam 3 (here, sucha configuration may then be reconfigured by a third layer (L3) (e.g.,RRC) and/or L2 (e.g., MAC) and/or L1 (e.g., DCI)). When a specific “SRSbeam set” is thus configured and the specific SRS triggering message isreceived, the UE may operate to perform both SRS transmission for beam 2and SRS transmission for beam 3 to SRS resource(s) indicated by thecorresponding triggering (or configured in advance by interlocking withthe triggering).

In addition, a fallback mode power control scheme may bedefined/configured, which is applied when the same TRP Rx beam ismaintained by beam blockage or the like, but when only the UE Tx beamneeds to be changed. For example, during a UL beam sweeping process,while separate/independent power control parameter(s) for the secondbest beam (pair) are determined/configured/stored, the UE may beconfigured to initiate specific UL transmission (e.g., SRS transmission,PUCCH transmission, and/or PUSCH transmission) by the specific fallbackmode power control. As a more specific example, assumed is a state inwhich a first best Tx beam and/or Rx beam (pair), a second best Tx beamand/or Rx beam (pair), . . . , information in a specific direction aredetermined by specific UL beam management and the information isreported from the UE to the eNB or the information is provided from theeNB to the UE. Initially, transmission/reception with beamformingconsidering the 1st best Tx beam and/or Rx beam (pair) is started atspecific UL transmission (for example, SRS transmission, PUCCHtransmission, and/or PUSCH transmission) of the UE. In this case, whenretransmission occurs due to a failure of decoding in the receiver(e.g., the eNB) with respect to the transmission signal (e.g., the eNBfeeds back NACK), or the like, the fallback mode power control and/or anoperation of performing other beam-based transmission may bedefined/configured. In particular, in a system to which “synchronousHARQ” is applied, in a situation where a separate specificationscheduling grant for retransmission is not provided and isdefined/configured to start retransmission according to an appointedtimeline, a specific Tx beam and/or Rx beam and/or specific power offsetparameter(s) (including the P_offset_beam value for each retransmission)applied at n-th retransmission (n=1, 2, . . . ) is defined/configured ina specific pattern in advance to provide the information to the UE andthe UE may be configured/indicated to start the UL transmission based onthe information.

More specifically, in this case, a different method may be applieddepending on whether a target of the UL transmission is PUCCH or PUSCH.For example, in the PUCCH, the eNB uses/applies power controlparameter(s) (including a related P_offset_beam value (for eachretransmission)) when the 2nd best UE Tx beam is used with respect to aTRP Rx beam tailored to a 1st best (UL) beam pair and in the PUSCH, theeNB uses/applies power control parameter(s) (including a relatedP_offset_beam value (for each retransmission)) for a 2nd best UL beampair, that is, an associated configuration may be provided to the UE andthe UE may operate to initiate the corresponding transmission based onthe provided configuration.

A specific k-th best Tx and/or Rx beam (pair) applied when the fallbacktype transmission occurs (e.g., specific n-th retransmission) may beconfigured to have a relatively wider beam width. Therefore, the k-thbest Tx and/or Rx beam (pair) may be configured/applied for thecorresponding fallback purpose (e.g., a purpose for coping with erroroccurrence for the 1st best beam (pair)). Alternatively, a scheme ofconfiguring/restricting an operation by starting transmission by theaforementioned specific “beam switching” may also be applied during thefallback transmission (e.g., n-th retransmission).

1-5) Power Transmission Period

In general, it is expected that the amount of information conveyed viaUL data channel is much larger than UL control channel. Therefore, therequired power for the UL data channel transmission may be larger thanthat of the UL control channel. For the NR design, TDM is considered formultiplexing structure between UL data and control channels for latencyreduction, flexible UL/DL configuration, and analog beamforming. In casewhen UL data and control channels are multiplexed by TDM manner, it maybe necessary to handle power imbalance between those two differentchannels which may be relatively larger compared to current LTE.Moreover, considering various OFDM numerology (e.g. differentsub-carrier spacing or symbol duration) used for the NR, it is necessaryto handle the power transmission period between the UL data and thecontrol channel for certain numerology (e.g. large sub-carrier spacing).

It is desirable to consider additional features for UL power control inthe NR such as an analog beamforming operation and the powertransmission period.

1-6) Per-TRP and Per-Layer Power Control

A coordinated transmission technique across multiple intra/inter-TRPs isdiscussed. Especially for high frequency bands in the NR, the number ofdominant rays per TRP or single panel may be limited (e.g., mostlyobserved by up to rank 2). Therefore, in order to achieve high SingleUser-MIMO (SU-MIMO) spectral efficiency, coordinated transmissionschemes across multiple TRPs need to be thoroughly investigated in theNR, including Coordinated MultiPoint (CoMP), Dynamic Point Selection(DPS), and independent-layer Joint Transmission (JT). When a DL-relatedDCI indicates the transmission rank and an applied coordinated scheme,the DCI decoding latency at the UE side may be one major problemwhenever analog beamforming is applied for a given time instance. Thisis because the DCI transmission may be conducted by a serving TRP butthe actual data transmission may be performed by another TRP as anexample.

In case of independent-layer JT where particular layer(s) may betransmitted from different TRPs, the corresponding UL transmission powerper layer-group may need to be configured and controlled by gNB, sinceat least the pathloss from different TRPs may be different. Further,separated UL power control process targeting different TRPs needs to befurther studied in the UL-CoMP context.

UL power control per TRP and per layer-group needs to be furtherinvestigated, at least for properly supporting DPS and independent-layerJT in the NR.

Hereinafter, a UL beam-specific power control method in the NR will bedescribed.

The following agreements are made on UL power control:

i) For beam specific power control, the NR defines beam specific openand closed loop parameters.

Here, details on “beam specific”, especially regarding handlinglayer/layer-group/panel specific/beam group specific/beam pair linkspecific power control will be discussed afterwards.

ii) gNB is aware of the power headroom differences for differentwaveforms, if the UE may be configured for different waveforms. Thedetails of offset and power control parameters (e.g., P_c, Max or otheropen/closed loop parameter will be discussed afterwards.

iii) Codebook based transmission for UL is supported at least bysignaling the following information in UL grant:

-   -   Sounding Resource Indicator (SRI)+Transmit Precoding Matrix        Indicator (TPMI)+Transmit Rank Indicator (TRI)

Here, TPMI is used to indicate a preferred precoder over the SRS port(s)in the SRS resource selected by the SRI.

If a single SRS resource is configured, there is no SRI. In this case,TPMI is used to indicate a preferred precoder over the SRS port in thesingle configured SRS resource.

-   -   Selection of multiple SRS resources is supported.

A proposal according to the present invention for beam-specific UL powercontrol will be described based on the above agreements.

It has been agreed to support differentiation of beam-specific open andclosed loop parameters between different beams for a UE since therequired power for UL performance would be different per beam for a UE.

However, especially for accumulative TPC procedures, it needs to befurther studied whether PC parameter separation per beam is superiorcompared with a common TPC accumulation process regardless of beamchanges or switching. The latter means that the TPC accumulation processwill not be reset even though a serving beam is changed by a beammanagement procedure, considering that the already stabilized transmitpower level is desired to remain as much as possible unless such beamchanges occur to a different TRP.

Per targeted service (e.g., URLLC and eV2X requiring higher reliability,there may be a configurable additional power offset to be applied on theTPC accumulation process whenever beam change or switching occurs withinthe same TRP so as to alleviate potential power control mismatch due tothe beam change/switching.

For accumulative TPC procedures, a configurable additional power offsetto be applied on a common TPC accumulation process needs to beconsidered, whenever beam change or switching occurs within the sameTRP, depending on a targeted service (e.g., URLLC and eV2X) requiringhigher reliability.

Regarding Open Loop Power Control (OLPC), proper DL RS such as aSynchronization Signal (SS) block (PBCH DMRS) and CSI-RS for pathlosscompensation should be defined at least for UEs supporting beamcorrespondence. Considering UL-CoMP operations, different DL RS forpathloss compensation can be configured per SRS resource for UL CSIacquisition.

For example, the above proposed contents may be applied as follows:

-   -   PL_c(q_d) is downlink pathloss in dB, which is calculated by the        UE by using a reference signal (RS) resource q_d with respect to        a serving cell c.

Here, the UE may be configured with the number of RS resources by higherlayer parameter (e.g., ‘num-pusch-pathlossReference-rs’) indicating thenumber of PUSCH pathloss reference RSs.

In addition, each set of RS configurations for the number of RSresources may be provided by a higher layer parameter (e.g.,pusch-pathloss-Reference-rs) indicating PUSCH pathloss reference RS.Here, the higher layer parameter (e.g., pusch-pathloss-Reference-rs)indicating PUSCH pathloss reference RS may include one or both of a setof SS/PBCH block indexes provided by a higher layer parameter (e.g.,‘pusch-pathlossReference-SSB) indicating a PUSCCH pathloss referencesynchronization signal block (SSB) and a set of CSI-RS configurationindexes provided by a higher layer parameter (e.g.,‘pusch-pathlossReference-CSIRS’) indicating PUSCH pathloss referenceCSI-RS.

The UE may identify an RS resource in the set of RS resources tocorrespond to the SS/PBCH block or to the CSI-RS configuration as aninformation (value) provided by a higher layer parameter (e.g.,‘pusch-pathlossreference-index’) indicating a PUSCH pathloss referenceindex.

If the UE is configured by higher layer parameter (e.g.,‘SRS-SpatialRelationInfo’) a mapping between a set of SRS resources anda set of RS resources for obtaining a downlink pathloss estimate, the UEuses the RS resources indicated by a value of a SRI in a DCI format(e.g., DCI format 0_0 or DCI format 0_1) that schedules the PUSCHtransmission to obtain the downlink pathloss estimate. That is, when aparameter (e.g., SRS-SpatialRelationInfo) indicating the SRS spatialrelation information set to the higher layer indicates one CSI-RS or oneSSB, the UE may apply the parameter to calculation of the pathloss (PL).

In addition, the parameter may be configured (or set) for each SRSresource or SRS resource set (for example, higher layer signaling (RRC,etc.)) as described above.

The RRC parameters may be set as shown in Table 6 below.

TABLE 6 SRS-SpatialRelationInfo Configuration of spatial relationIncluded in SRS- between reference RS and target ResourceConfig RS.Reference RS is SSB/CSI-RS/SRS. num-pusch- The number of DL RSpathlossReference-rs configurations for measuring pathloss Individualpathloss estimations are maintained by the UE and used for PUSCH powercontrol, for each configuration. N RS configurations may be configured.When a PUSCH beam indication is present, N is 1, 2, 3, or 4 andotherwise, N = 1 pusch-pathlossReference- Configuration (e.g., CSI-RSrs-config configuration or SS block) to be used for PUSCH pathlossestimation N RS configurations may be configured.pusch-pathlossReference- Present in pusch- SSB pathlossReference-rs-config pusch-pathlossReference- Present in pusch- CSIRSpathlossReference- rs-config pusch-pathlossReference- Present in pusch-rs pathlossReference- rs-config pathlossreference-index Indexcorresponding to each RS Present in pusch- of the PL reference RSpathlossReference- configuration rs-config

However, the above operation may be limited to be applicable only whenthe higher layer parameter (e.g., “SRS-SpatialRelationInfo”) indicatingthe SRS spatial relation information indicates one CSI-RS or one SSB.That is, if the higher layer parameter (e.g., “SRS-SpatialRelationInfo”)indicating the SRS spatial relation information indicates one (another)SRS resource (this case may correspond to a case “without beamcorrespondence”), an operation may be defined/configured/indicated,which calculates the pathloss based on a DL RS such as a separatelyconfigured or preconfigured DL RS (e.g., one CSI-RS or one SSB) (and/or,e.g., determined by a predefined/configured function or rule based on adefault type of the DL RS such as an SS block (PBCH DMRS) or a set ofconfigured CSI-RSs) as proposed below.

And/or if the parameter (“SRS-SpatialRelationInfo”) indicating the SRSspatial relation information indicates one (another) SRS resource asdescribed above, when the indicated SRS resource itself is configured,if the parameter (“SRS-SpatialRelationInfo”) indicating theseparate/independent SRS spatial relation information indicates oneCSI-RS or one SSB, this may be applied in the path loss calculation.That is, a parameter (“SRS-SpatialRelationInfo”) indicating the SRSspatial relation information, which is a sub-parameter for the SRSresource itself indicated by the SRI field in the DCI, indicates one(another) SRS resource (UL beam management (for Beam Management (BM)),if a parameter (“SRS-SpatialRelationInfo”) indicating the SRS spatialrelation information, which is a sub-parameter for this resource,indicates one CSI-RS or one SSB, it is possible to indicate the DL RSspanning multiple stages in such a method in which the parameter isapplied to the pathloss calculation. This indirect indication scheme maybe generalized in such a manner that one (another) continued SRSresource is reached over several stages as indicated, so that theindicated specific DL RS is applied to the pathloss calculation.

For a UE without beam correspondence, pathloss compensation may beperformed by the predefined/configured function or rule based on thedefault type of the DL RS, such as the SS block (PBCH DMRS) and/or theset of configured CSI-RSs. In other words, the UE may calculate adownlink path loss estimation value via RSRP calculated using the DL RS(e.g., SS block and/or CSI-RS) and calculate uplink power as inversecompensation based on the downlink pathloss estimation value.

That is, such DL RS (e.g., SS block (PBCH DMRS) and/or a set ofconfigured CSI-RSs) information may be configured separately for the UE(e.g., by RRC, MAC CE and/or DCI). Then, the UE may perform the pathlosscompensation operation based thereon.

And/or even if the DL RS information is not separately configured by theeNB, the UE may perform the pathloss compensation operation based onspecific DL RS (e.g., the SS block (PBCH DMRS) and/or the set ofconfigured CSI-RSs) for the serving cell. In this case, for example, thespecific DL RS may correspond to at least one DL RS (reported previouslyor last) that has default DL RS or a lowest (or highest) index (whensorted to an average power level (e.g., RSRP)) or a best power levelbased on information based thereon.

And/or, at the same time, a specific calculation function such as amaximum operation or a specific weighted average function may bedefined/configured. For example, a max function or some weightedaveraging functions may be defined to perform the pathloss compensationfor the cases of without beam correspondence.

Therefore, for OLPC, proper DL RS for the pathloss compensation shouldbe defined or configured per SRS resource. In addition, apredefined/configured function for the pathloss compensation should bedetermined for the UE without the beam correspondence.

In regard to transmission for codebook based transmission for UL, theSRI in UL grant may indicate selection of multiple SRS resources.

The multiple SRS resources may support multi-panel joint transmission inUL. Furthermore, each panel transmission associated with each indicatedSRS resource may target different UL reception points (RPs) in thecontext of UL-CoMP.

To properly support this, the NR network should be able to at leastcalculate accurate MCS per different layer group corresponding todifferent SRS resources (or different SRS sets (groups)), with aseparated power control process per SRS resource.

Therefore, multiple ULPC processes for the UE need to be supported, andeach ULPC process may be associated with at least one SRS resourceconfigured to the UE.

For example, configured SRS resource identifiers (IDs) #1 and #2 may beassociated to the same ULPC process A, while another configured SRSresource ID #3 may be associated to other ULPC process B. ULPC processesA and B may target different reception points.

That is, the ULPC process may mean that the same parameter (e.g., adB-unit power value (P0) indicated by the eNB for the uplink powercontrol, reference signal (e.g., SSB, CSI-RS, etc.) information used forestimating the downlink pathloss to be calculated by the UE, an alphavalue by which the downlink pathloss estimation value calculated by theUE is multiplied in order to compensate for the downlink pathlossestimation) is used for the power control of uplink transmission (i.e.,uplink reference signal (e.g., SRS) and uplink channel (e.g., PUSCH andPUCC)). Therefore, in the above example, one or more SRS resourcesassociated with the same ULPC process may mean that the same powercontrol parameter is applied when the UE transmits the SRS in thecorresponding SRS resource. Consequently, in the above example, one ULPCprocess may be associated with one or more SRS resources and when theone or more SRS resources are grouped into the SRS resource set (group),it may be appreciated that parameters for the power control areindividually set for each SRS resource set. That is, according to theabove description, it may be interpreted that SRSs #1 and #2 belong toone SRS resource set (group), and as a result, a parameter for commonpower control may be applied.

In addition, the SRS resources #1 and #2 which follow the same ULPCprocess A may be dynamically selected by the SRI indication in UL grant.That is, on which SRS resource the UE should transmit the SRS betweenthe SRS resources #1 and #2 which belong to one SRS resource set may beindicated to the UE by the SRI field in the UL grant.

For example, when SRS resources #1 and #3 are jointly indicated by theSRI field in the UL grant, this may be interpreted as alayer-group-separated UL multi-panel transmission operation or a UL-CoMPjoint reception operation at the gNB side.

In this case, independent power control may be performed for eachindicated SRS resource. And/or the rank/layer number may be indicatedseparately (in the same UL grant) for each indicated SRS resource.And/or (separate) TPMI information tailored thereto may be provided foreach indicated SRS resource (in the same UL grant). That is, in thiscase, since SRS resources (i.e., SRS resources #1 and #3) which belongto different SRS resource sets (groups) are simultaneously indicated tothe UE, it may be interpreted that the independent power control isperformed for each SRS resource.

In other words, a plurality of SRS resources (i.e., belonging todifferent SRS resource sets, i.e., associated with different TRPs) maybe indicated simultaneously by one SRI field in the UL grant, and foreach of the plurality of SRS resources, different layer groups may beconfigured. In this case, the parameter set for the power control of thePUSCH may be individually determined for each layer group.

Consequently, to properly support multi-panel UL transmission andUL-CoMP operations, multiple ULPC processes (i.e., multiple SRS resourcesets (groups) to which the same power control parameter is applied foreach SRS resource set (group)) for the UE should be supported and eachULPC process (i.e., each SRS resource set (group)) may be associatedwith at least one SRS resource configured to the UE.

In the above description, for convenience of description, two SRSresource sets (groups) are assumed and two SRS resources are indicatedthrough one SRI field. However, this is for convenience of descriptionand the present invention is not limited thereto.

Hereinafter, a UL transmission power control method in the NR will bedescribed.

The following agreements are made on UL power control:

i) NR supports beam specific pathloss for ULPC.

ii) The following DL RS may be used for pathloss (PL) calculation forULPC.

-   -   If the power offset between SSS and DM-RS for PBCH is known by        the UE, both SSS of the SS block and DM-RS for PBCH are used.    -   If the power offset between SSS and DM-RS for PBCH is not known        by the UE, only the SSS of SS block is used.    -   CSI-RS is used.

iii) In aperiodic SRS transmission triggered by a single aperiodic SRStriggering field, the UE may be configured to transmit N (N>1) SRSresources for UL beam management.

Hereinafter, the UL power control method in the NR will be describedbased on the above agreements.

It has been agreed to support differentiation of beam-specific open andclosed loop parameters between different beams for the UE in the NRsince the required power for UL performance is different per beam for aUE.

However, especially for accumulative TPC procedures, it needs to befurther studied whether PC parameter separation per beam is superiorcompared with a common TPC accumulation process regardless of beamchanges or switching. The latter means that the TPC accumulation processwill not be reset even though a serving beam is changed by a beammanagement procedure, considering that the already stabilized transmitpower level is desired to remain as much as possible unless such beamchanges occur to a different TRP.

Per targeted service (e.g., URLLC and eV2X requiring higher reliability,there may be a configurable additional power offset to be applied on theTPC accumulation process whenever beam change or switching occurs withinthe same TRP so as to alleviate potential power control mismatch due tothe beam change/switching.

For accumulative TPC procedures, a configurable additional power offsetto be applied on a common TPC accumulation process needs to beconsidered, whenever beam change or switching occurs within the sameTRP, depending on a targeted service (e.g., URLLC and eV2X) requiringhigher reliability.

In respect to the OLPC, considering the UL-CoMP operations, different DLRS for pathloss compensation can be configured per SRS resource for ULCSI acquisition. For a UE without beam correspondence, pathlosscompensation may be performed by the predefined/configured function orrule based on the default type of the DL RS, such as the SS block (PBCHDMRS) and/or the set of configured CSI-RSs. For example, a max functionor some weighted averaging functions may be defined to perform thepathloss compensation in the case of without beam correspondence.

In the OLPC, a predefined/configured function for the pathlosscompensation should be determined for the UE without the beamcorrespondence.

Considering the agreements regarding codebook based transmission for UL,SRI in UL grant may indicate selection of multiple SRS resources, whichcan support multi-panel joint transmission in UL. Furthermore, eachpanel transmission associated with each indicated SRS resource maytarget different UL reception points (RPs) in the context of UL-CoMP. Toproperly support this, NR network should be able to at least calculateaccurate MCS per different layer group corresponding to different SRSresource, with also separated power control process per SRS resource. Ingeneral, multiple ULPC processes for the UE need to be supported, andeach ULPC process may be associated with at least one SRS resource(and/or at least DL RS/SS for the OLPC as described above) configured tothe UE.

In addition/alternatively, specific corresponding configured DL RS/SS(s)to be subjected to OLPC per ULPC process may be switched to anotherRS/SS (e.g., via MAC CE and/or DCI). In addition/alternatively,(one-time) additional power offset/bias values to be applied at thistime may be indicated (together) (to extend to a larger range than thenormal TPC range) and the UE may be defined/configured/indicated toreflect the additional power offset/bias values to TPC accumulation. Forexample, configured SRS IDs #1 and #2 may be associated to the same ULPCprocess A, while another configured SRS resource ID #3 may be associatedto other ULPC process B. ULPC processes A and B may target differentreception points. In addition, the SRS resources #1 and #2 which followthe same ULPC process A may be dynamically selected by the SRIindication in UL grant. For example, when SRS resources #1 and #3 arejointly indicated by the SRI field in the UL grant, this may beinterpreted as a layer-group-separated UL multi-panel transmissionoperation or a UL-CoMP joint reception operation at the gNB side.

Consequently, to properly support multi-panel UL transmission andUL-CoMP operations, multiple ULPC processes (i.e., multiple SRS resourcesets (groups) to which the same power control parameter is applied foreach SRS resource set (group)) for the UE should be supported and eachULPC process (i.e., each SRS resource set (group)) may be associatedwith at least one SRS resource configured to the UE.

In addition/alternatively, groups of specific ULPC process(s) configuredexplicitly/implicitly as described above may share Closed Loop PowerControl (CLPC), so that when the UE performs uplink power control, theUE may be defined/configured to apply/accumulate the TPC accumulationtogether. For example, the OLPC may be separated/divided (independently)for each process, but the CLPC may be configured to be shared. Inaddition/alternatively, the OLPC as well as the CLPC may be configuredto be independently separated/divided and applied for each processor.

In addition/alternatively, when scheduling specific UL data (i.e., aPUSCH) in a specific UL grant to the eNB, it is possible to explicitlyindicate transmission of UL data (i.e., PUSCH) according to a certainULPC process (i.e., the uplink power control is performed by applying aparameter set for specific power control) in the corresponding UL grant.That is, a field for explicitly indicating which ULPC is applied toperform UL data transmission may be included in the UL grant.

In addition/alternatively, the UE may be implicitly indicated to followthe specific ULPC process at the time of the power control of scheduledUL data (i.e., PUSCH) by interlocking with a specific existing DCI field(or value) (e.g., an HARQ identifier (ID)). In other words, depending onthe existing DCI field (or value), it may be implicitly indicated whichparameter set for the power control is to be used.

For example, a specific HARQ ID value may interlock with a specific ULPCidentifier (ID) in advance (e.g., via RRC and/or MAC CE). That is, themapping relationship between the HARQ ID and the ULPC ID may beconfigured in advance (for example, via RRC and/or MAC CE). In addition,the UE may transmit the uplink by determining the uplink transmissionpower by applying the interlocking ULPC process according to with whichHARQ ID the UE is scheduled by the DCI (i.e., applying the correspondingpower control parameter set).

In this case, as an example, the specific HARQ ID(s) may be associatedwith a specific independent service type (e.g., eMBB or URLLC) and thusthere is an effect of allowing different power levels to be determinedfor each specific communication service type. For example, the URLLC maybe configured to transmit at a relatively higher power than the eMBB.

In other words, a form may be configured/applied in which a specificservice type (e.g., eMBB or URLLC) is linked in advance (for example,via RRC/MAC CE, etc.) for each specific HARQ ID(s). Therefore, it ispossible to initiate data-type specific scheduling by L1 signaling(e.g., by DCI, associated with HARQ ID) to transmit an uplink datapacket for a specific service type (e.g., eMBB or URLLC).

In addition/alternatively, a specific ULPC may be implicitly indicatedby interlocking with a specific existing DCI field (value) (e.g., theSRI field described above). In other words, depending on the SRI field(or value), which parameter set for the uplink power control is to beused may be implicitly indicated.

For example, a specific SRI field value (e.g. indicating SRSresource(s)) may interlock with a specific ULPC ID in advance (e.g., RRCand/or MAC CE). That is, the mapping relationship between the SRI fieldvalue and the ULPC ID may be configured in advance (for example, via RRCand/or MAC CE). In addition, the UE may determine the uplinktransmission power and transmit the uplink by applying the correspondinginterlocking ULPC process (i.e., applying the uplink power controlparameter set) according to which SRI(s) value is indicated andscheduled by the DCI.

In this case, as an example, the specific SRI(s) value may be associatedwith the uplink transmission panel(s) of a specific UE and/or the targetreception point(s) of the eNB. Therefore, there is an effect that theeNB provides the flexibility to allow the UE to perform uplinktransmission at different power levels by different ULPC processes.

In addition/alternatively, through a form such as a specific common DCI(e.g., transmitted on a common search space (CSS), for example, a formsimilar to LTE DCI 3/3A), each ULPC process may be mapped to anindependent state and/or UE index (e.g., a specific RNTI value).Accordingly, for which ULPC process TPC (accumulation) is to beperformed may be transmitted at a time (to multiple UEs) (in the CSSformat).

As a result, in an example of the most flexible method among theabove-mentioned methods, the eNB may independently inform the UE ofwhich target RP/beam and/or UE Tx panel is indicated through individualSRI fields. At the same time, it may be indicated separately what powercontrol to apply via the individual specific ULPC process indicators anddepending on which service type (e.g., indicated via RRC and/or MAC CE)uplink data is to be transmitted may be indicated through specificindividual service-type indicators. High flexibility of the uplinkscheduling combination may be supported by using the separatelyindicated types or the like.

Regarding N (>1) aperiodic SRS transmission triggered by singleaperiodic SRS triggering field, an issue on transmission power for the NSRS resources for UL beam management may be resolved in general byproper UL power control mechanisms as mentioned above per configured SRSresource (group).

For example, gNB may associate specific N SRS resources to the same ULPCprocess. Then the same transmission power may be guaranteed for the NSRS resources for beam management. An additional method may bediscussed, for configuring the triggering state description by RRCand/or MAC CE to override the current transmission power level per SRSresource according to associated ULPC process. This is to enforce thesame Tx power level for N SRS resources regardless of current ULPCprocess(es) (e.g., applying the highest current SRS Tx power to one of NSRS resources similarly to other N−1 SRS resources). That is, even ifthere is a specific ULPC process that is already followed for each SRSresource for determining the transmission power for the N (>1) aperiodicSRS resources to be triggered together, the UE may beconfigured/indicated to (additionally) perform at least one operationdescribed below (in addition to information indicating which specific Nresources or not basically) in a description (e.g., configured via RRCand/or MAC CE) regarding an operation which the UE is to perform whenthe corresponding triggering state itself may be dynamically indicated.

-   -   Like a scheme of “applying the highest current SRS Tx power to        one of N SRS resources similarly to other N−1 SRS resources”        described above, when there are N power values determined        according to the current ULPC process with respect to N SRS        resources, respectively, N corresponding SRS transmission powers        may be configured to be equal to a specific value among the N        power values. Here, the specific value may include is the        largest value (or the smallest value for reducing interference        with (other cell), etc.) among the N power values determined        according to the ULPC process or a value (e.g., average,        weighted average, etc.) calculated through a specific        defined/configured function to yield a representative power        value with the N power values. In addition/alternatively, after        the power level is equalized, if the power level exceeds a        maximum power amount (e.g., P_c_MAX) that may be maximally        transmitted, the power level may be configured to be scaled down        according to a corresponding restriction value all at once. In        addition/alternatively, if a power sharing rule is        defined/configured, which is to be applied to signals (e.g.,        PUCCH, PUSCH, etc.) to be transmitted to another specific        uplink, the target power level to be scaled down may be set to a        target power level according to the power sharing rule/to which        the power sharing rule is to be applied.    -   As another scheme, not in a scheme of calculating a specific        “highest power level” and setting the target power level to the        highest power level described above, the same power level may be        configured to be set to “full power” applicable (even though        there are specific ULPC process(es) applied for each SRS        resource (group) unit at present, continuously by disregarding        the specific ULPC process(es)) with respect to the N SRS        resources all at once (i.e., overriding). In        addition/alternatively, after the power level is equalized, if        the power level exceeds a maximum power amount (e.g., P_c_MAX)        that may be maximally transmitted, the power level may be        configured to be scaled down according to a corresponding        restriction value all at once. In addition/alternatively, if a        power sharing rule is defined/configured, which is to be applied        to signals (e.g., PUCCH, PUSCH, etc.) to be transmitted to        another specific uplink, the target power level to be scaled        down may be set to a target power level according to the power        sharing rule/to which the power sharing rule is to be applied.    -   As yet another scheme, not in the scheme of calculating a        specific “highest power level” and setting the target power        level to the highest power level described above, even though        there are specific ULPC process(es) applied for each SRS        resource (group) unit at present, by disregarding the specific        ULPC process(es), the same power level may be configured to be        set to a specific “predefined/preconfigured power level/value”        to be continuously applied when (N) SRS resources for specific        UL beam management are to be together transmitted (and/or a        power level/value determined by the OLPC (and in association        even with specific representative CLPC) with respect to specific        predefined/preconfigured DL RS and/or specified representative        DL RS) all at once (overriding). Here, the specified        representative DL RS may include (serving) SS block DMRS (i.e.,        for PBCH) (by initial access/random access channel (RACH)        procedure and/or beam management (BM) procedure) and/or SSS        and/or specific (e.g., lowest-index) CSI-RS. In        addition/alternatively, after the power level is equalized, if        the power level exceeds a maximum power amount (e.g., P_c_MAX)        that may be maximally transmitted, the power level may be        configured to be scaled down according to a corresponding        restriction value all at once. In addition/alternatively, if a        power sharing rule is defined/configured, which is to be applied        to signals (e.g., PUCCH, PUSCH, etc.) to be transmitted to        another specific uplink, the target power level to be scaled        down may be set to a target power level according to the power        sharing rule/to which the power sharing rule is to be applied.    -   As still yet another scheme, when there is at least one specific        (link adaptation (LA)) ULPC process which is maintained        (activated) (with respect to a specific beam) at present, the        uplink transmission may be configured to be performed by setting        a specific power value determined by the ULPC process to the        same power level for the N SRS resources (and/or by adding a        specific configured/indicated single power offset thereto) all        at once. In other words, this means that the power level        determined by the normal link adaptation ULPC (e.g., associated        with PUSCH PC) (plus P_SRS_offset) is applied to the        transmission of SRS resource(s) for beam management as it is and        the same power is applied even to a beam management SRS resource        corresponding to a different (analog) beam pair from the link        adaptation SRS resource among them. This is to indicate        transmission of the beam management SRS resources in order to        test which beam pair among beam pairs other than the current        serving beam pair in a situation in which the beam management        SRS resources are transmitted. Further, the reason is that it        may be still meaningless to configure an individual ULPC process        among the beam management (N) SRS resources. In summary, the        individual ULPC processes may be configured/applied among the        link adaptation SRS resource(s), but the individual ULPC        processes (or a separate ULPC process separated from link        adaptation) may not be configured among the beam management SRS        resource(s). In addition/alternatively, after the power level is        equalized, if the power level exceeds a maximum power amount        (e.g., P_c_MAX) that may be maximally transmitted, the power        level may be configured to be scaled down according to a        corresponding restriction value all at once. In        addition/alternatively, if a power sharing rule is        defined/configured, which is to be applied to signals (e.g.,        PUCCH, PUSCH, etc.) to be transmitted to another specific        uplink, the target power level to be scaled down may be set to a        target power level according to the power sharing rule/to which        the power sharing rule is to be applied.

Even when the specific aperiodic SRS triggering state is configured totransmit specific M (>=1) SRS resources (for CSI acquisition) as well asthe specific N SRS resources (for beam management) (i.e., when thespecific aperiodic SRS triggering state is configured to simultaneouslytransmit a total of N+M SRS resources), at least one of the proposedmethods may be applied in a such a manner of replacing N in the aboveproposed schemes with “N+M”. That is, in this case, even in a case whereSRS resources for different purposes are mixed as well as a case whereonly the beam management SRS resources are together transmitted, the SRSresources may be transmitted by applying the specific power level (i.e.,the same specific power) like the method proposed above by disregarding(i.e., overriding) the situation in which each ULPC process is appliedby such a scheme.

Alternatively, it may be restricted/configured that at least one of theabove proposals is applied only to N without replacing N in the proposedschemes with “N+M” as described above. That is, N+M SRS resources aretogether transmitted, but only N SRS resources among them may betransmitted by applying the specific power level (e.g., the samespecific power) only the transmission power for N SRS resources like theproposed method. In addition, simultaneously, M SRS resource(s) may betransmitted while applying the power level power-controlled according tothe specific ULPC process associated with M corresponding SRS resources(in advance), respectively to the transmission power of the other M SRSresource(s) as they are. This is caused by a difference in purpose ofthe SRS transmission.

Further, in the above proposed methods, it may be interpreted that themost is described based on a fact that both N and/or M SRS resources areaperiodic SRS types, but it is apparent that at least one of the schemesproposed in the present invention above may be extensively applied evento a case where some of them are semi-persistent SRS types and/orperiodic SRS types. That is, the scheme may be applied only to the samespecific SRS transmission instance and even though the multiple specificSRS resources are scattered and transmitted to different SRStransmission instances, the SRS transmission may be performed byoverriding a part of determination of the transmission power by thealready interlocking ULPC process(es) and applying the power control forsome multiple SRS resources to the specific power level (e.g., to thesame specific power) (only temporarily/during a specific interval).

In addition/alternatively, with respect to the at least one proposalmethod, an operation (this may be interpreted as power controladjustment) that performs SRS transmission by overriding to the specificpower level (e.g., the same specific power) may be temporarily appliedonly to a specific SRS transmission interval (cycle). That is, inaddition, the SRS transmission may be configured to be performed atanother independent specific power level (e.g., at the same specificpower) with respect to another SRS transmission interval (cycle). Thepower control adjustment may be performed independently for eachspecific interval (cycle).

For example, at least one operation in the above-described method may betemporarily applied only to an interval of “one round of SRS beamsweeping”. In addition, at least one operation in the above-describedanother independent method may be defined to be applied orconfigured/indicated to the UE by the eNB with respect to a next/anotherinterval of “one round of SRS beam sweeping”.

FIG. 13 is a diagram illustrating a method for transmitting andreceiving an uplink according to an embodiment of the present invention.

Referring to FIG. 13, the UE receives SRS configuration controlinformation (DCI) from the eNB (S1301).

Here, the SRS configuration information may include a parameter set(including, e.g., a default power value P0, an inverse compensationinformation/ratio α, a downlink reference signal forestimation/calculation of pathloss, etc.) for power control of SRS foreach SRS resource set and the SRS resource set may include one or moreSRS resources.

The UE determines transmission power of the SRS based on the parameterset of the power control of the SRS (S1302).

Here, the transmission power of the SRS may be determined based on thedownlink pathloss estimation value calculated by the UE using thedownlink reference signal indicated by the parameter set for the powercontrol of the SRS. In this case, the downlink reference signal may beindicated by higher layer signaling (RRC or MAC CE). For example, thedownlink reference signal may include SSB and CSI-RS.

In addition, the downlink reference signal may be changed by signaling(e.g., MAC CE, DCI, etc.) transmitted by the eNB.

Further, the UE may determine the transmission power of the SRS bycommonly applying TPC accumulation to an SRS resource set (e.g., for aspecific SRS resource set (group) configured explicitly/implicitly).

A power control adjustment for adjusting the transmission power of theSRS may be independently applied for each specific SRS transmissioninterval. Here, when the power control adjustment is triggered,transmission power values of the SRS on all SRS resources may beadjusted equally regardless of determination of the transmission powerof the SRS. Specifically, an operation of performing the SRStransmission by overriding at specific power level (e.g., at the samespecific power) may be temporarily applied only to a specific SRStransmission interval (cycle). In addition, the SRS transmission may beconfigured to be performed at another independent specific power level(e.g., at the same specific power) with respect to another SRStransmission interval (cycle). Further, when the adjusted transmissionpower value exceeds a predetermined value, the adjusted transmissionpower value may be scaled down all at once.

The UE transmits the SRS to the eNB with the determined transmissionpower (S1303).

Although not illustrated in FIG. 13, an operation for controlling anoperation for transmitting an uplink channel (PUSCH and PUCCH)/anoperation for controlling transmission power of the uplink channel maybe performed in conjunction with the SRS transmission/receptionoperation in FIG. 13.

Specifically, the UE receives downlink control information (DCI)including physical uplink shared channel (PUSCH) scheduling informationfrom the eNB. Here, the DCI may include a SRS resource indicator (SRI).In addition, the UE determines the PUSCH transmission power based on theparameter set for the power control of the PUSCH determined from theSRI.

In this case, the UE may receive from the eNB one or more parameter sets(e.g., a default power value P0, an inverse compensationinformation/ratio α, a downlink reference signal forestimating/calculating pathloss, etc.) for the power control of thePUSCH and calculate the PUSCH transmission power based on the parameterset indicated by the SRI.

Further, when a plurality of SRS resources is indicated by the SRI, anddifferent layer groups are configured with respect to the plurality ofSRS resources, respectively, the parameter set for the power control ofthe PUSCH may be individually determined for each layer group.

Even in this case, the transmission power of the PUSCH may be determinedbased on the downlink pathloss estimation value calculated by the UEusing the downlink reference signal indicated by the parameter set forthe power control of the PUSCH. Further, the downlink reference signalmay be changed by signaling (MAC CE, DCI, etc.) transmitted by the eNB.In addition, the UE transmits the PUSCH to the eNB with the determinedtransmission power.

On the other hand, when information on the downlink reference signal isnot provided from the eNB (for example, when the SRI in the DCI is notincluded), the pathloss estimation value may be calculated by using aspecific downlink reference signal (e.g., a downlink reference signalhaving a relatively highest power level).

Overview of Devices to which Present Invention is Applicable

FIG. 14 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present invention.

Referring to FIG. 14, a wireless communication system includes a basestation 1410 and multiple UEs 1410 positioned within an area of the basestation 1420.

The eNB 1410 includes a processor 1411, a memory 1412, and a transceiveror a radio frequency (RF) unit 1413. The processor 1411 implements afunction, a process, and/or a method which are proposed in FIGS. 1 to 13above. Layers of a radio interface protocol may be implemented by theprocessor 1411. The memory 1412 is connected with the processor 1411 tostore various pieces of information for driving the processor 1411. TheRF unit 1413 is connected with the processor 1411 to transmit and/orreceive a radio signal.

The UE 1420 includes a processor 1421, a memory 1422, and an RF unit1423. The processor 1421 implements a function, a process, and/or amethod which are proposed in FIGS. 1 to 13 above. Layers of a radiointerface protocol may be implemented by the processor 1421. The memory1422 is connected with the processor 1421 to store various pieces ofinformation for driving the processor 1421. The RF unit 1423 isconnected with the processor 1421 to transmit and/or receive a radiosignal.

The memories 1412 and 1422 may be positioned inside or outside theprocessors 1411 and 1421 and connected with the processors 1411 and 1421by various well-known means. Further, the eNB 1410 and/or the UE 1420may have a single antenna or multiple antennas.

The embodiments described so far are those of the elements and technicalfeatures being coupled in a predetermined form. So far as there is notany apparent mention, each of the elements and technical features shouldbe considered to be selective. Each of the elements and technicalfeatures may be embodied without being coupled with other elements ortechnical features. In addition, it is also possible to construct theembodiments of the present invention by coupling a part of the elementsand/or technical features. The order of operations described in theembodiments of the present invention may be changed. A part of elementsor technical features in an embodiment may be included in anotherembodiment, or may be replaced by the elements and technical featuresthat correspond to other embodiment. It is apparent to constructembodiment by combining claims that do not have explicit referencerelation in the following claims, or to include the claims in a newclaim set by an amendment after application.

The embodiments of the present invention may be implemented by variousmeans, for example, hardware, firmware, software and the combinationthereof. In the case of the hardware, an embodiment of the presentinvention may be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicro controller, a micro processor, and the like.

In the case of the implementation by the firmware or the software, anembodiment of the present invention may be implemented in a form such asa module, a procedure, a function, and so on that performs the functionsor operations described so far. Software codes may be stored in thememory, and driven by the processor. The memory may be located interioror exterior to the processor, and may exchange data with the processorwith various known means.

It will be understood to those skilled in the art that variousmodifications and variations may be made without departing from theessential features of the inventions. Therefore, the detaileddescription is not limited to the embodiments described above, butshould be considered as examples. The scope of the present inventionshould be determined by reasonable interpretation of the attachedclaims, and all modification within the scope of equivalence should beincluded in the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention has been described based on an example in which itis applied to the 3GPP LTE/LTE-A systems or 5G systems, but may beapplied to various wireless communication systems in addition to the3GPP LTE/LTE-A systems or 5G system.

1. A method for uplink transmission by a User Equipment (UE) in awireless communication system, comprising: receiving, from a basestation, Sounding Reference Signal (SRS) configuration information,wherein the SRS configuration information includes a parameter set forpower control of SRS for each SRS resource set and the SRS resource setincludes one or more SRS resources; determining a transmission power ofthe SRS, based on the parameter set for power control of the SRS; andtransmitting the SRS to the base station.
 2. The method of claim 1,wherein the transmission power of the SRS is determined, based on adownlink path-loss estimation value calculated by the UE using adownlink reference signal indicated by the parameter set for the powercontrol of the SRS.
 3. The method of claim 2, wherein the downlinkreference signal includes Synchronization Signal Block (SSB) and ChannelState Information-Reference Signal (CSI-RS).
 4. The method of claim 2,wherein the downlink reference signal is changed by a Medium AccessControl-Control Element (MAC-CE) transmitted by the base station.
 5. Themethod of claim 1, wherein the transmission power of the SRS isdetermined by applying a Transmit Power Control (TPC) accumulationcommonly to the SRS resource set.
 6. The method of claim 1, wherein apower control adjustment for adjusting the transmission power of the SRSis applied independently for each specific SRS transmission interval. 7.The method of claim 6, wherein, when the power control adjustment istriggered, all of transmission power values of the SRS are identicallyadjusted on all SRS resources, regardless of the transmission power ofthe SRS being determined.
 8. The method of claim 7, wherein, when theadjusted transmission power value exceeds a predetermined value, theadjusted transmission power value is scaled down collectively.
 9. Themethod of claim 1, further comprising: receiving, from the base station,downlink control information (DCI) including Physical Uplink SharedChannel (PUSCH) scheduling information, wherein the DCI includes a SRSResource Indicator (SRI); determining a PUSCH transmission power basedon a parameter set for power control of PUSCH determined from the SRI;and transmitting the PUSCH to the base station.
 10. The method of claim9, wherein, when a plurality of SRS resources are indicated by the SRIand a layer group is configured differently for each of the plurality ofSRS resources, a parameter set for power control of the PUSCH isrespectively determined for each layer group.
 11. The method of claim 9,wherein the transmission power of the PUSCH is determined, based on adownlink path-loss estimation value calculated by the UE using adownlink reference signal indicated by the parameter set for the powercontrol of the PUSCH.
 12. The method of claim 11, wherein the downlinkreference signal is changed by a Medium Access Control-Control Element(MAC-CE) transmitted by the base station.
 13. The method of claim 1,further comprising: determining a transmission power of Physical UplinkShared Channel (PUSCH) based on a downlink path-loss estimation valuecalculated by the UE using a downlink reference signal; and transmittingthe PUSCH to the base station; wherein, when information for thedownlink reference signal is not provided by the base station, thepath-loss estimation value is calculated using a downlink referencesignal having a relatively largest power level.
 14. A User equipment(UE) performing uplink transmission in a wireless communication system,comprising: a transceiver for transmitting and receiving a radio signal;and a processor for controlling the transceiver, wherein the processoris configured to: receive, from a base station, Sounding ReferenceSignal (SRS) configuration information, wherein the SRS configurationinformation includes a parameter set for power control of SRS for eachSRS resource set and the SRS resource set includes one or more SRSresources; determine a transmission power of the SRS, based on theparameter set for power control of the SRS; and transmit the SRS to thebase station.